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  Subjects -> ELECTRONICS (Total: 193 journals)
Showing 1 - 200 of 277 Journals sorted alphabetically
Acta Electronica Malaysia     Open Access  
Advanced Materials Technologies     Hybrid Journal  
Advances in Electrical and Electronic Engineering     Open Access   (Followers: 7)
Advances in Electronics     Open Access   (Followers: 94)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Power Electronics     Open Access   (Followers: 39)
Advancing Microelectronics     Hybrid Journal  
Aerospace and Electronic Systems, IEEE Transactions on     Hybrid Journal   (Followers: 349)
American Journal of Electrical and Electronic Engineering     Open Access   (Followers: 26)
Annals of Telecommunications     Hybrid Journal   (Followers: 9)
APSIPA Transactions on Signal and Information Processing     Open Access   (Followers: 9)
Archives of Electrical Engineering     Open Access   (Followers: 14)
Australian Journal of Electrical and Electronics Engineering     Hybrid Journal  
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Batteries     Open Access   (Followers: 7)
Batteries & Supercaps     Hybrid Journal  
Bell Labs Technical Journal     Hybrid Journal   (Followers: 30)
Bioelectronics in Medicine     Hybrid Journal  
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 22)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 38)
Biomedical Instrumentation & Technology     Hybrid Journal   (Followers: 6)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 13)
BULLETIN of National Technical University of Ukraine. Series RADIOTECHNIQUE. RADIOAPPARATUS BUILDING     Open Access   (Followers: 1)
Bulletin of the Polish Academy of Sciences : Technical Sciences     Open Access   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 47)
China Communications     Full-text available via subscription   (Followers: 9)
Chinese Journal of Electronics     Hybrid Journal  
Circuits and Systems     Open Access   (Followers: 15)
Consumer Electronics Times     Open Access   (Followers: 5)
Control Systems     Hybrid Journal   (Followers: 306)
ECTI Transactions on Computer and Information Technology (ECTI-CIT)     Open Access  
ECTI Transactions on Electrical Engineering, Electronics, and Communications     Open Access   (Followers: 1)
Edu Elektrika Journal     Open Access   (Followers: 1)
Electrica     Open Access  
Electronic Design     Partially Free   (Followers: 123)
Electronic Markets     Hybrid Journal   (Followers: 7)
Electronic Materials Letters     Hybrid Journal   (Followers: 4)
Electronics     Open Access   (Followers: 104)
Electronics and Communications in Japan     Hybrid Journal   (Followers: 10)
Electronics For You     Partially Free   (Followers: 103)
Electronics Letters     Hybrid Journal   (Followers: 26)
Elkha : Jurnal Teknik Elektro     Open Access  
Embedded Systems Letters, IEEE     Hybrid Journal   (Followers: 55)
Energy Harvesting and Systems     Hybrid Journal   (Followers: 4)
Energy Storage     Hybrid Journal  
Energy Storage Materials     Full-text available via subscription   (Followers: 3)
EPE Journal : European Power Electronics and Drives     Hybrid Journal  
EPJ Quantum Technology     Open Access   (Followers: 1)
EURASIP Journal on Embedded Systems     Open Access   (Followers: 11)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Communications and Information Theory     Full-text available via subscription   (Followers: 6)
Foundations and Trends® in Signal Processing     Full-text available via subscription   (Followers: 10)
Frequenz     Hybrid Journal   (Followers: 1)
Frontiers of Optoelectronics     Hybrid Journal   (Followers: 1)
Geoscience and Remote Sensing, IEEE Transactions on     Hybrid Journal   (Followers: 209)
Haptics, IEEE Transactions on     Hybrid Journal   (Followers: 4)
IACR Transactions on Symmetric Cryptology     Open Access  
IEEE Antennas and Propagation Magazine     Hybrid Journal   (Followers: 100)
IEEE Antennas and Wireless Propagation Letters     Hybrid Journal   (Followers: 81)
IEEE Journal of Emerging and Selected Topics in Power Electronics     Hybrid Journal   (Followers: 51)
IEEE Journal of the Electron Devices Society     Open Access   (Followers: 9)
IEEE Journal on Exploratory Solid-State Computational Devices and Circuits     Hybrid Journal   (Followers: 1)
IEEE Power Electronics Magazine     Full-text available via subscription   (Followers: 75)
IEEE Transactions on Antennas and Propagation     Full-text available via subscription   (Followers: 73)
IEEE Transactions on Automatic Control     Hybrid Journal   (Followers: 58)
IEEE Transactions on Circuits and Systems for Video Technology     Hybrid Journal   (Followers: 26)
IEEE Transactions on Consumer Electronics     Hybrid Journal   (Followers: 44)
IEEE Transactions on Electron Devices     Hybrid Journal   (Followers: 19)
IEEE Transactions on Information Theory     Hybrid Journal   (Followers: 26)
IEEE Transactions on Power Electronics     Hybrid Journal   (Followers: 78)
IEEE Transactions on Signal and Information Processing over Networks     Full-text available via subscription   (Followers: 12)
IEICE - Transactions on Electronics     Full-text available via subscription   (Followers: 12)
IEICE - Transactions on Information and Systems     Full-text available via subscription   (Followers: 5)
IET Cyber-Physical Systems : Theory & Applications     Open Access   (Followers: 1)
IET Energy Systems Integration     Open Access  
IET Microwaves, Antennas & Propagation     Hybrid Journal   (Followers: 35)
IET Nanodielectrics     Open Access  
IET Power Electronics     Hybrid Journal   (Followers: 57)
IET Smart Grid     Open Access  
IET Wireless Sensor Systems     Hybrid Journal   (Followers: 18)
IETE Journal of Education     Open Access   (Followers: 4)
IETE Journal of Research     Open Access   (Followers: 11)
IETE Technical Review     Open Access   (Followers: 13)
IJEIS (Indonesian Journal of Electronics and Instrumentation Systems)     Open Access   (Followers: 3)
Industrial Electronics, IEEE Transactions on     Hybrid Journal   (Followers: 74)
Industrial Technology Research Journal Phranakhon Rajabhat University     Open Access  
Industry Applications, IEEE Transactions on     Hybrid Journal   (Followers: 38)
Informatik-Spektrum     Hybrid Journal   (Followers: 2)
Instabilities in Silicon Devices     Full-text available via subscription   (Followers: 1)
Intelligent Transportation Systems Magazine, IEEE     Full-text available via subscription   (Followers: 13)
International Journal of Advanced Research in Computer Science and Electronics Engineering     Open Access   (Followers: 18)
International Journal of Advances in Telecommunications, Electrotechnics, Signals and Systems     Open Access   (Followers: 11)
International Journal of Antennas and Propagation     Open Access   (Followers: 11)
International Journal of Applied Electronics in Physics & Robotics     Open Access   (Followers: 4)
International Journal of Computational Vision and Robotics     Hybrid Journal   (Followers: 5)
International Journal of Control     Hybrid Journal   (Followers: 11)
International Journal of Electronics     Hybrid Journal   (Followers: 7)
International Journal of Electronics and Telecommunications     Open Access   (Followers: 13)
International Journal of Granular Computing, Rough Sets and Intelligent Systems     Hybrid Journal   (Followers: 3)
International Journal of High Speed Electronics and Systems     Hybrid Journal  
International Journal of Hybrid Intelligence     Hybrid Journal  
International Journal of Image, Graphics and Signal Processing     Open Access   (Followers: 16)
International Journal of Microwave and Wireless Technologies     Hybrid Journal   (Followers: 10)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields     Hybrid Journal   (Followers: 4)
International Journal of Power Electronics     Hybrid Journal   (Followers: 25)
International Journal of Review in Electronics & Communication Engineering     Open Access   (Followers: 4)
International Journal of Sensors, Wireless Communications and Control     Hybrid Journal   (Followers: 10)
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 4)
International Journal of Wireless and Microwave Technologies     Open Access   (Followers: 6)
International Transaction of Electrical and Computer Engineers System     Open Access   (Followers: 2)
JAREE (Journal on Advanced Research in Electrical Engineering)     Open Access  
Journal of Biosensors & Bioelectronics     Open Access   (Followers: 4)
Journal of Advanced Dielectrics     Open Access   (Followers: 1)
Journal of Artificial Intelligence     Open Access   (Followers: 11)
Journal of Circuits, Systems, and Computers     Hybrid Journal   (Followers: 4)
Journal of Computational Intelligence and Electronic Systems     Full-text available via subscription   (Followers: 1)
Journal of Electrical and Electronics Engineering Research     Open Access   (Followers: 35)
Journal of Electrical Bioimpedance     Open Access  
Journal of Electrical Bioimpedance     Open Access   (Followers: 2)
Journal of Electrical Engineering & Electronic Technology     Hybrid Journal   (Followers: 7)
Journal of Electrical, Electronics and Informatics     Open Access  
Journal of Electromagnetic Analysis and Applications     Open Access   (Followers: 8)
Journal of Electromagnetic Waves and Applications     Hybrid Journal   (Followers: 9)
Journal of Electronic Design Technology     Full-text available via subscription   (Followers: 6)
Journal of Electronics (China)     Hybrid Journal   (Followers: 5)
Journal of Energy Storage     Full-text available via subscription   (Followers: 4)
Journal of Engineered Fibers and Fabrics     Open Access   (Followers: 2)
Journal of Field Robotics     Hybrid Journal   (Followers: 3)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 182)
Journal of Information and Telecommunication     Open Access   (Followers: 1)
Journal of Intelligent Procedures in Electrical Technology     Open Access   (Followers: 3)
Journal of Low Power Electronics     Full-text available via subscription   (Followers: 10)
Journal of Low Power Electronics and Applications     Open Access   (Followers: 10)
Journal of Microelectronics and Electronic Packaging     Hybrid Journal  
Journal of Microwave Power and Electromagnetic Energy     Hybrid Journal   (Followers: 3)
Journal of Microwaves, Optoelectronics and Electromagnetic Applications     Open Access   (Followers: 11)
Journal of Nuclear Cardiology     Hybrid Journal  
Journal of Optoelectronics Engineering     Open Access   (Followers: 4)
Journal of Physics B: Atomic, Molecular and Optical Physics     Hybrid Journal   (Followers: 30)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 11)
Journal of Semiconductors     Full-text available via subscription   (Followers: 5)
Journal of Sensors     Open Access   (Followers: 26)
Journal of Signal and Information Processing     Open Access   (Followers: 9)
Jurnal ELTIKOM : Jurnal Teknik Elektro, Teknologi Informasi dan Komputer     Open Access  
Jurnal Rekayasa Elektrika     Open Access  
Jurnal Teknik Elektro     Open Access  
Jurnal Teknologi Elektro     Open Access  
Kinetik : Game Technology, Information System, Computer Network, Computing, Electronics, and Control     Open Access  
Learning Technologies, IEEE Transactions on     Hybrid Journal   (Followers: 12)
Magnetics Letters, IEEE     Hybrid Journal   (Followers: 7)
Majalah Ilmiah Teknologi Elektro : Journal of Electrical Technology     Open Access   (Followers: 2)
Metrology and Measurement Systems     Open Access   (Followers: 6)
Microelectronics and Solid State Electronics     Open Access   (Followers: 28)
Nanotechnology Magazine, IEEE     Full-text available via subscription   (Followers: 42)
Nanotechnology, Science and Applications     Open Access   (Followers: 6)
Nature Electronics     Hybrid Journal   (Followers: 1)
Networks: an International Journal     Hybrid Journal   (Followers: 5)
Open Electrical & Electronic Engineering Journal     Open Access  
Open Journal of Antennas and Propagation     Open Access   (Followers: 9)
Optical Communications and Networking, IEEE/OSA Journal of     Full-text available via subscription   (Followers: 15)
Paladyn. Journal of Behavioral Robotics     Open Access   (Followers: 1)
Power Electronics and Drives     Open Access   (Followers: 2)
Problemy Peredachi Informatsii     Full-text available via subscription  
Progress in Quantum Electronics     Full-text available via subscription   (Followers: 7)
Pulse     Full-text available via subscription   (Followers: 5)
Radiophysics and Quantum Electronics     Hybrid Journal   (Followers: 2)
Recent Advances in Communications and Networking Technology     Hybrid Journal   (Followers: 3)
Recent Advances in Electrical & Electronic Engineering     Hybrid Journal   (Followers: 9)
Research & Reviews : Journal of Embedded System & Applications     Full-text available via subscription   (Followers: 5)
Revue Méditerranéenne des Télécommunications     Open Access  
Security and Communication Networks     Hybrid Journal   (Followers: 2)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 56)
Semiconductors and Semimetals     Full-text available via subscription   (Followers: 1)
Sensing and Imaging : An International Journal     Hybrid Journal   (Followers: 2)
Services Computing, IEEE Transactions on     Hybrid Journal   (Followers: 4)
Software Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 78)
Solid State Electronics Letters     Open Access  
Solid-State Circuits Magazine, IEEE     Hybrid Journal   (Followers: 13)
Solid-State Electronics     Hybrid Journal   (Followers: 9)
Superconductor Science and Technology     Hybrid Journal   (Followers: 3)
Synthesis Lectures on Power Electronics     Full-text available via subscription   (Followers: 3)
Technical Report Electronics and Computer Engineering     Open Access  
TELE     Open Access  
Telematique     Open Access  
TELKOMNIKA (Telecommunication, Computing, Electronics and Control)     Open Access   (Followers: 9)
Transactions on Electrical and Electronic Materials     Hybrid Journal  
Universal Journal of Electrical and Electronic Engineering     Open Access   (Followers: 6)
Ural Radio Engineering Journal     Open Access  
Visión Electrónica : algo más que un estado sólido     Open Access   (Followers: 1)
Wireless and Mobile Technologies     Open Access   (Followers: 6)
Wireless Power Transfer     Full-text available via subscription   (Followers: 4)
Women in Engineering Magazine, IEEE     Full-text available via subscription   (Followers: 11)
Електротехніка і Електромеханіка     Open Access  

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Similar Journals
Journal Cover
Magnetics Letters, IEEE
Journal Prestige (SJR): 0.532
Citation Impact (citeScore): 2
Number of Followers: 7  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1949-307X
Published by IEEE Homepage  [191 journals]
  • Flexible Control of Magnetic Fields by Shaped-Optimized Three-Dimensional
           Coil Arrays
    • Authors: Ali Abdolali;Ali Mohtadi Jafari;
      Pages: 1 - 5
      Abstract: The synthesis of desired low-frequency magnetic fields is of high importance in electromagnetic design. The use of coil arrays (CAs) is among the most effective methods for realizing a desired field. However, in designing CAs, researchers are faced with a lack of design parameters. At low frequencies, the design parameters are usually limited to the size and phase of the source and the size and position of the coils. In this letter, with the help of three-dimensional (3-D) coils, the spatial current distribution, i.e., the shape of coils, is added to the design parameters of the CA problem. This novel 3-D coil array creates a high degree of freedom for the synthesis of the desired magnetic field which cannot be achieved by ordinary coil arrays or a single 3-D coil. The technological advances in the field of 3-D printing helps in the fabrication of these 3-D structures with high precision, low cost, and fast prototyping. In the design process, dyadic Green's functions are used to analytically calculate the magnetic field. Then, in order to define the shape of the 3-D coils, these shapes are extended based on the proper basis functions. By determining the coefficients of these basis functions by means of optimization methods, the shape of each 3-D coil in the array is obtained. This method is used to realize an arbitrary magnetic field along a line by means of a single-source array that includes three 3-D coils. The designed array is implemented with the use of fused-deposition-modeling 3-D printing. The design results, numerical simulations, and experimental tests demonstrate a high degree of accuracy in the fabrication process and the ability of 3-D arrays to synthesize magnetic fields.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Precise Model-Free Spline-Based Approach for Magnetic Field Mapping
    • Authors: Federico Ongaro;Christoff Marthinus Heunis;Sarthak Misra;
      Pages: 1 - 5
      Abstract: Untethered magnetic manipulation has found applications in a rapidly increasing number of fields, ranging from minimally invasive surgery to assembly of industrial microelectromechanical systems. Despite this relevance, present-day literature on precise magnetic mapping is sparse, especially for magnetic fields affected by external disturbances. In this letter, we address this deficiency by introducing a model-free mapping technique. Remarkably, the presented spline-based approach is capable of addressing the presence of inhomogeneous static disturbances and the mapping of nonazimuthally symmetric electromagnets. This work is validated with the mapping of nine metal-core electromagnets in the presence of inhomogeneous static disturbances. A grid of 5120 measurements is collected by a custom-programed robotic arm and used for mapping. The values predicted by the approach are compared against 3430 independent field measurements with an R2 value of 0.9884 and maximum relative errors of 7%. Overall, this spline-based approach provides a flexible technique for the precise mapping of electromagnetic fields and gradients even when, for reasons regarding coil shape or disturbances, the electromagnetic field does not present any axial symmetry.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Electromagnetic Position Sensing and Force Feedback for a Magnetic Stylus
           With an Interactive Display
    • Authors: Peter Berkelman;Bernadette Tix;Hamza Abdul-Ghani;
      Pages: 1 - 5
      Abstract: This letter describes the design, implementation, validation, and demonstration of an electromagnetic system that can be incorporated into a graphical display to provide computer-controlled planar feedback forces on the tip of a stylus or fingertip-mounted magnet held near the display surface, according to the magnet position and virtual fixtures implemented in software. An array of magnetometer sensors is used to detect the position of the magnet, while a pair of box-shaped coils behind the display produces feedback forces on the stylus parallel to the plane of the display. Electromagnetic analysis for the system design is presented and system implementation is described. Validation results are given for force generation within a 100 mm × 100 mm area and force interaction with a virtual obstacle is demonstrated.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Experimental Validation of a Frequency-Selective Surface-Loaded Hybrid
           Metamaterial Absorber With Wide Bandwidth
    • Authors: Atipriya Sharma;Ravi Panwar;Rajesh Khanna;
      Pages: 1 - 5
      Abstract: The achievement of wide absorption bandwidth for a single-layer metamaterial absorber remains a challenge. In this letter, a frequency-selective surface (FSS), single-substrate layer, broadband metamaterial absorber is investigated theoretically, experimentally, and by simulation in the frequency range of 2-18 GHz. Simulations of the reflection coefficient of the absorber with different substrate dielectric thicknesses, FSS thicknesses, and FSS dimensions indicate that there exist optimal values for the absorber design. The measured results from a fabricated prototype are in close agreement with the simulations, suggesting the effectiveness of the structure for actual electromagnetic applications. The fabricated absorber with thickness 2.0 mm has a minimum reflection coefficient of -29.0 dB at 12.2 GHz. The -10 dB absorption bandwidth is 7.5 GHz in the range of 8.5-16 GHz. Effective complex electromagnetic parameters are extracted to quantitatively understand the absorption. A miniaturized structure, single-substrate layer, simple geometry, and wide bandwidth are some of the key features of the proposed metamaterial absorber.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Frequency Response of a Moving Two-Dimensional Defect in Magnetic Flux
           Leakage Inspection
    • Authors: Mustafa Makki Aziz;Reyah Abdulla;Mohamad Al-Dujaili;
      Pages: 1 - 4
      Abstract: The detection of magnetic flux leakage (MFL) enables nondestructive detection and characterization of defects in magnetic structures. In this letter, Fourier transforms of the leakage fields from a two-dimensional surface defect are evaluated to produce analytical expressions for the frequency response of MFL signals detected by a flux-sensitive sensor. The expressions show the correlation between the spectral response of the leakage fields, defect dimensions, and sensing element lift-off spacing as a product of frequency-dependent defect-width loss function, spacing loss function, and thickness enhancement function. The lower and upper band edges of the band-limited leakage magnetic fields are theoretically identified. A spectral method for sizing of defects is proposed based on the frequency response.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetic Localization for an Electromagnetic-Based Haptic Interface
    • Authors: Alaa Adel;Mohanad Mansour;Mina M. Micheal;Ahmed Abdelmawla;Islam S. M. Khalil;Sarthak Misra;
      Pages: 1 - 5
      Abstract: In this letter, we develop a magnetic localization system for an electromagnetic-based haptic interface (EHI). Haptic interaction is achieved using a controlled magnetic force applied via an EHI on a magnetic dipole attached to a wearable finger splint. The position of the magnetic dipole is estimated using two identical arrays of three-dimensional magnetic field sensors in order to eliminate the magnetic field generated by the EHI. The measurements of these arrays are used to estimate the position of the magnetic dipole by an artificial neural network. This network maps the field readings to the position of the magnetic dipole. The proposed system is experimentally validated under four cases of the magnetic field generated by the EHI. These cases are likely to be encountered during the haptic rendering of virtual shapes. In the absence of the magnetic field, the mean absolute position error (MAE) is 0.80 ± 0.30 mm (n = 125). Static and sinusoidal magnetic fields are applied, and the MAEs are 1.26 ± 0.43 mm (n = 125) and 0.91 ± 0.33 mm (n = 125), respectively. A random time-varying magnetic field is applied, and the MAE is 0.86 ± 0.33 mm (n = 125). Our statistical analysis shows that the repeatability of the magnetic localization is acceptable regardless of the field generated by the EHI, at α = 0.05 and 95% confidence level.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Development of a Coil Driver for Magnetic Manipulation Systems
    • Authors: Mert Kaya;Uthvag Sakthivel;Islam S. M. Khalil;Sarthak Misra;
      Pages: 1 - 5
      Abstract: Pulsewidth modulation (PWM) is the most commonly used technique to drive electromagnetic coils in magnetic manipulation systems. Relatively low PWM frequencies generate high-magnitude current ripple and magnetic field fluctuation. In this letter, coils are powered by a driver at PWM frequencies close to their self-resonant frequencies to generate high-frequency magnetic fields and minimize current ripple and magnetic field fluctuation. In order to protect the driver against the penetration of stray electromagnetic and magnetic fields, a multilayer shielding enclosure is employed. The coil driver is used to study the effect of varying PWM frequencies on current, magnetic field, and ohmic loss using Helmholtz, air, and iron core coils. The current ripple magnitude is significantly minimized when the coils are driven at PWM frequencies close to their self-resonant frequencies. This results in reduction of magnetic field fluctuation and provides more accurate measurement of magnetic field magnitude. Our experiments show that increasing the PWM frequency from 100 Hz to 25 kHz decreases the current ripple and magnetic fluctuation by two orders of magnitude, with a negligible effect on the ohmic loss.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magneto-Electric Hybrid Generator for Simultaneously Harvesting Vibration
           and Stray Magnetic Field Energy
    • Authors: Wei He;Aichao Yang;Jitao Zhang;Chiwen Qu;
      Pages: 1 - 4
      Abstract: An array-based magneto-electric hybrid generator is presented which can respond to vibration and stray magnetic fields. Using the magnetic levitation mechanism, the generator can extract vibration energy in three axes, and the use of a magneto-electric array improves the output power. The nonlinear magnetic force on the suspending magnets is analyzed during vibration, and a nonlinear dynamical equation is established. A law for the time-varying displacement of the suspending magnets is obtained after solving the dynamical equation. The magnetic field on the magneto-electric transducer array under dual excitations is analyzed, and a theoretical model is developed. A prototype is fabricated to conduct the energy-harvesting experiments. The results demonstrate the feasibility of the generator under dual excitations.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Subsurface Corrosion Detection in Industrial Steel Structures
    • Authors: Roberta Guilizzoni;Graeme Finch;Stuart Harmon;
      Pages: 1 - 5
      Abstract: Corrosion is a central problem for the oil and gas and nuclear industries, affecting pipelines and nuclear waste storage tanks. Reliable methods for timely corrosion detection and integrity evaluation are needed for a range of industrial structures where corrosion under insulation manifests as wall loss. Commercially available detection systems cannot be used in harsh nuclear-storage environments. Moreover, these systems are not reliable for detecting the inner wall thickness of industrial structures made of multiple layers of material, including insulation layers. A novel nondestructive testing method based on low-frequency eddy-current induction was developed and tested on a multilayered steel structure, including an insulating gap. The method enables through-wall thickness measurements between 4 and 16 mm, with a measurement error of 1 mm. The technique is quantitative, nondestructive, and allows the sensor coil to be positioned on the outside of the composite steel structure, which is useful when the interior of an industrial container or pipeline is not accessible.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • $text{Bi}_{0.90}text{Nd}_{0.10}text{Fe}_{0.98}TM_{0.02}text{O}_{3}$ +( $TM=+text{Mn}$ ,+Co,+Ni,+and+Cu)+Materials&rft.title=Magnetics+Letters,+IEEE&rft.issn=1949-307X&rft.date=2019&rft.volume=10&rft.spage=1&rft.epage=5&rft.aulast=Minh;&rft.aufirst=Dao&rft.au=Dao+Viet+Thang;Nguyen+Manh+Hung;Du+Thi+Xuan+Thao;Le+Thi+Mai+Oanh;Do+Danh+Bich;Nguyen+Cao+Khang;Van+Quang+Nguyen;Nguyen+Van+Minh;">Structural, Electrical, and Magnetic Properties of
           $text{Bi}_{0.90}text{Nd}_{0.10}text{Fe}_{0.98}TM_{0.02}text{O}_{3}$ ( $TM=
           text{Mn}$ , Co, Ni, and Cu) Materials
    • Authors: Dao Viet Thang;Nguyen Manh Hung;Du Thi Xuan Thao;Le Thi Mai Oanh;Do Danh Bich;Nguyen Cao Khang;Van Quang Nguyen;Nguyen Van Minh;
      Pages: 1 - 5
      Abstract: Pure BiFeO3 (BFO) and Bi0.90Nd0.10Fe0.98TM0.02O3 (TM = Mn, Co, Ni, and Cu) materials have been synthesized by the sol-gel method. Effects of codoping Nd and transition metal (TM) on the structural, electrical, and magnetic properties of BFO were investigated by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, scanning electron microscope (SEM), vibrating sample magnetometry, polarization vs. electric field hysteresis loops (P-E), and complex impedance spectra measurements. A distortion of crystal structure, in which lattice parameters a and c decreased in all codoped samples, was measured by XRD. SEM images showed a significant reduction of average grain size and an obvious change in surface morphology with Nd and TM codoping in BFO. Codoped samples demonstrated various improvements in ferroelectric and ferromagnetic properties, most notably for codoped (Nd and TM) samples. Saturation magnetization (Ms) and saturation dielectric polarization (Ps) increased from Ms = 0.060 emu/g, Ps = 1.03 μC/cm2 for pure BFO to Ms = 0.411 emu/g, Ps = 11.08 μC/cm2 for a codoped (Nd and Mn) sample. Our results show that Mn is the best TM for codoping with Nd in BFO to improve its multiferroic properties.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetic Separation of Volatile Solid Particles Based on Field-Induced
           Translational Motion Under Short-Duration Microgravity Conditions
    • Authors: Wakana Yamaguchi;Keiji Hisayoshi;Chiaki Uyeda;Kentaro Terada;
      Pages: 1 - 4
      Abstract: We designed an improved apparatus to separate and identify volatile solid particles at temperatures around 200 K using short-duration microgravity. Separation is based on the difference in diamagnetism of the mixed particles released in a region of monotonically decreasing magnetic field. The velocity of the translating particles in the microgravity region is considerably enhanced, which yields improved accuracy in measurement of the terminal velocity of the particles outside the magnetic field region. We achieved separation of a mixture of heterogeneous particles, including solid CO2, with high resolution. A particle's composition can be estimated from the value of magnetic susceptibility obtained from the terminal velocity because the particle's acceleration induced by the magnetic volume force is independent of particle mass. It is expected that material abundances of heterogeneous, volatile, solid particles, such as hexagonal ice, dry ice, ethane, methane, and CO, can be determined in this simple manner in cold regions on Earth and in the outer regions of the solar system.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Enhanced Magnetic Softness of Double-Layered Perovskite Manganite
           La1.7Gd0.3SrMn2O7
    • Authors: Subrata Das;Irin Sultana;M. D. I. Bhuyan;M. A. Basith;
      Pages: 1 - 4
      Abstract: Bulk polycrystalline samples of Gd-doped La2-xGdxLa2-xGdxSrMn2O7SrMn2O7 (x = 0.3, 0.6) double-layered perovskite manganites were synthesized in air by conventional solid-state reaction and then annealed at 600 °C in inert (N2) atmosphere. Rietveld refined powder X-ray diffraction patterns show impurity peaks for samples synthesized in air, whereas annealing completely removes the undesired peaks in the lightly doped (15% Gd) sample and partially removes them in the heavily doped (30% Gd) sample. The morphology was improved in both samples due to annealing. Magnetic hysteresis loops demonstrate enhanced magnetic softness for the lightly doped manganite. Its saturation magnetization at room temperature at 10 kOe is 50 emu/g, and is increased to 53 emu/g after heat treatment. Heat treatment also decreases its coercive field and remanent magnetization. These properties indicate that 15% Gd-doped La1.7Gd0.3SrMn2O7 manganite may be used in applications where magnetic softness is desired.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetic Field Sensor Based on a Conical Frustum of Terfenol-D Composite
    • Authors: R. Esteban Jiménez-Mejía;Chiu Tai Law;Rodrigo Acuna Herrera;
      Pages: 1 - 4
      Abstract: This letter presents the theoretical and experimental analysis of a magnetic field sensor based on the interaction of a conical frustum of magnetostrictive composite with an embedded fiber Bragg grating (FBG) along its axis. The possibility of tailoring a nonuniform-induced strain along the FBG through magnetostriction enables the inference of the magnetic field with both wavelength shift and optical power measurements. Strain coupling interaction and power reflectance of the FBG were modeled and showed a very good agreement with experimental data.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Activation of Microwave Signals in Nanoscale Magnetic Tunnel Junctions by
           Neuronal Action Potentials
    • Authors: Jose Miguel Algarin;Bharath Ramaswamy;Lucy Venuti;Matthews E. Swierzbinski;James Baker-McKee;Irving N. Weinberg;Yu-Jin Chen;Ilya N. Krivorotov;Jordan A. Katine;Jens Herberholz;Ricardo C. Araneda;Benjamin Shapiro;Edo Waks;
      Pages: 1 - 5
      Abstract: Action potentials are the basic unit of information in the nervous system, and their reliable detection and decoding holds the key to understanding how the brain generates complex thought and behavior. Transduction of these signals into microwave signal oscillations can enable wireless sensors that report on brain activity through magnetic induction. In this letter, we demonstrate that action potentials from the lateral giant neurons of crayfish can induce microwave oscillations in nanoscale magnetic tunnel junctions (NMTJs). We show that action potentials activate microwave oscillations in NMTJs with an amplitude that follows the action potential signal, demonstrating that the device has both the sensitivity and temporal resolution to respond to action potentials from a single neuron. The activation of magnetic oscillations by action potentials, together with the small surface area and the high-frequency tunability, makes these devices potential candidates for high-resolution sensing of bioelectric signals from neural tissues. These device attributes may be useful for the design of high-throughput bidirectional brain–machine interfaces.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Transcranial Magnetic Stimulation: Development of a Novel Deep-Brain
           Triple-Halo Coil
    • Authors: Priyam Rastogi;Erik Gordan Lee;Ravi L. Hadimani;David C. Jiles;
      Pages: 1 - 5
      Abstract: Transcranial magnetic stimulation (TMS) is a noninvasive treatment for major depressive disorder. TMS coil design plays an important role in maximizing the magnetic field strength at the required location in the brain. Development of deep-brain TMS coils to stimulate subcortical structures will expand the uses of TMS beyond the simulation of superficial cortical targets. The simulation of deep-brain regions may have beneficial effects on neurological disorders such as Parkinson's disease, posttraumatic stress disorder, and mild traumatic brain injury. In this letter, a multicoil configuration, the triple-halo coil (THC), which can stimulate deep brain structures such as the hippocampus and amygdala, is designed and tested. A finite element tool is used to determine the induced electric field and magnetic field in these regions due to the THC alone and in combination with a figure-of-8 coil. Analysis of the results is done with the help of an anatomically accurate heterogeneous head model of a 34-year-old man derived from magnetic resonance imaging. The magnetic field of the THC is measured and compared with the simulated field.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Stress Effects in the Brain During Transcranial Magnetic Stimulation
    • Authors: Abas Sabouni;Mahsa Khamechi;Marc Honrath;
      Pages: 1 - 4
      Abstract: We used a three-dimensional magnetic resonance image to model the Lorentz force in scalp, skull, cerebrospinal fluid, gray matter, and white matter of the human brain during transcranial magnetic stimulation (TMS). The simulations show that during TMS procedures, measurable intracranial forces develop within different tissue layers of the brain. This force strongly depends on the strength of the magnetic field generated by the TMS coil. The effect of this force will cause stress in the brain tissues and creates around 5%-10% deformation in both gray and white matter.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Single Triangular Coil Used to Identify the Position and Orientation of a
           Subject for Biomagnetic Measurements
    • Authors: Yoshiaki Adachi;Daisuke Oyama;Gen Uehara;
      Pages: 1 - 5
      Abstract: Knowledge of the position and orientation of a subject in reference to an array of magnetic flux sensors is crucial for accurate current source reconstruction in biomagnetic field measurements. For alignment between the subject and the sensor array, multiple small circular marker coils, attached to anatomical fiducial points on the body's surface, are commonly used. We propose a new triangular marker coil that can replace the conventional marker coils. A triangular marker coil is effective for continuous positioning because, unlike conventional marker coils, it requires neither sequential excitation nor multiple oscillators. In this letter, a suitable design for triangular marker coils was investigated, and the positioning of an actual triangular marker coil using a magnetoencephalogram system was demonstrated.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Dry Phantoms With Deep Signal Sources for Magnetoencephalography
    • Authors: Daisuke Oyama;Yoshiaki Adachi;Gen Uehara;
      Pages: 1 - 5
      Abstract: We developed dry phantoms with signal source depth of 2.5, 12.5, and 22.5 mm for magnetoencephalography (MEG) systems. Their calibration was based on three-dimensional measurements and numerical calculations. The positions of the effective equivalent current dipoles (ECDs) were shifted 0.1 to 0.9 mm from their designed positions, and uncertainties in calibration were about 0.17 mm. An experimental evaluation of an MEG system gave displacements of the measured ECDs of 0.6±0.3, 0.8±0.3, and 0.9±0.3 mm for the three signal source depths. Thus, the signal source localization accuracy of our MEG system was within about 1 mm for deep signal sources.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Novel Production of Magnetite Particles via Thermochemical Processing of
           Digestate From Manure and Food Waste
    • Authors: Diana Rodriguez Alberto;Kristen Stojak Repa;Swati Hegde;Casey W. Miller;Thomas A. Trabold;
      Pages: 1 - 5
      Abstract: Sustainable management of food waste has become a global priority because of the significant environmental impacts associated with conventional disposal methods, including landfilling. Thermochemical processing is a food-waste-to-energy conversion technology in which food waste materials are converted to biofuel in a reduced O2 environment at elevated temperatures. Another conversion technology is anaerobic digestion, in which microorganisms digest biodegradable material, producing biofuel and solid byproducts “digestate.” We measured the physical properties of “biochar” produced by combining these approaches: digestate was used as feedstock for a commercial-scale thermochemical processing system. Magnetite (Fe3O4) particles were produced during the food-waste-to-energy conversion process. This was particularly unexpected because none of the input materials were ferromagnetic, and no specific Fe precursors were introduced in the process. The Fe3O4 was identified through a combination of X-ray fluorescence and dc magnetometry. Zero-field cooled magnetization-temperature curves reveal a Verwey transition at ~125 K across samples prepared under various conditions. Room temperature magnetization-field loops show a Langevin-like curve, technical saturation, and coercive fields of HC = 98-130 Oe across various samples. Clear Verwey transition, room temperature hysteresis, and an irreversibility temperature well above room temperature indicate that particles are multidomain. We attribute the presence of Fe3O4 to the relatively high concentration of Fe naturally present in the solid digestate and the operating parameters of the thermochemical conversion process. High surface area magnetic biochar has a variety of potential applications, including the adsorption of heavy metals, wastewater treatment, supercapacit-rs, and conductive polymer composites.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Torque Optimization for Voltage-Controlled Magnetic Tunnel Junctions as
           Memory and Stochastic Signal Generators
    • Authors: Albert Lee;Di Wu;Kang L. Wang;
      Pages: 1 - 4
      Abstract: We propose an optimization principle for the operation of voltage-controlled magnetic tunnel junctions (VC-MTJs): optimization via magnetic torque, in contrast to the conventional optimization via magnetization. For memory applications, we minimize the magnetic torque at the end of the write pulse, whereas for stochastic applications, we attempt to find a balance between damping and precessional torque at the beginning of the pulse. We simulate the method using a physics-based VC-MTJ model and show that, for memory applications, optimization for torque reduces ringing by 43% and improves pulse shape tolerance by a factor of 2.1, whereas for stochastic applications, it improves convergence time by 61% and energy by 37%.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnonic Band Structure Established by Chiral Spin-Density Waves in
           Thin-Film Ferromagnets
    • Authors: Patrick Sprenger;Mark A. Hoefer;Ezio Iacocca;
      Pages: 1 - 5
      Abstract: Recent theoretical studies have demonstrated the possibility to excite and sustain noncollinear magnetization states in ferromagnetic nanowires. The resulting state is referred to as a spin-density wave (SDW). SDWs can be interpreted as hydrodynamic states with a constant fluid density and fluid velocity in systems with easy-plane anisotropy. Here, we consider the effect of the nonlocal dipole field arising from the finite thickness of magnetic thin films on the spatial profile of the SDW and on the associated magnon dispersion. Utilizing a hydrodynamic formulation of the Larmor torque equation, it is found that the nonlocal dipole field modulates the fluid velocity. Such a modulation induces a magnonic band structure unlike the typical dispersion relation for magnons on uniform magnetization. The analytical results are validated by micromagnetic simulations. Band gaps on the order of gigahertz are numerically observed to depend on the SDW fluid velocity and film thickness for realistic material parameters. The presented results suggest that SDWs can find applications as reconfigurable magnonic crystals.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • The Longitudinal Spin Seebeck Coefficient of Fe
    • Authors: Zhihao Duan;Bingfeng Miao;Liang Sun;Di Wu;Jun Du;Haifeng Ding;
      Pages: 1 - 5
      Abstract: We report an experimental study of the longitudinal spin Seebeck effect (LSSE) of a Fe thin film with a Pt detection layer. By varying the Fe thickness, we find that the anomalous Nernst effect (ANE) of Fe changes sign and vanishes at about 4.8 nm. This provides a unique opportunity to study the LSSE where the influence of ANE is absent. The addition of a 3 nm Pt layer produces a considerable thermal voltage, which comes from the LSSE of Fe solely. The opposite signs of thermal voltages in Pt/Fe and W/Fe bilayer structures confirm that the signal is dominated by LSSE because Pt and W have opposite signs of spin Hall angle. In conjunction with the Pt-thickness-dependent measurement of effective spin-mixing conductance of Fe/Pt films, we estimate the spin Seebeck coefficient of Fe.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Low-Barrier Magnet Design for Efficient Hardware Binary Stochastic Neurons
    • Authors: Orchi Hassan;Rafatul Faria;Kerem Yunus Camsari;Jonathan Z. Sun;Supriyo Datta;
      Pages: 1 - 5
      Abstract: Binary stochastic neurons (BSNs) form an integral part of many machine learning algorithms, motivating the development of hardware accelerators for this complex function. It has been recognized that hardware BSNs can be implemented using low-barrier magnets (LBMs) by minimally modifying present-day magnetoresistive random-access memory (MRAM) devices. A crucial parameter that determines the response of these LBM-based BSN designs is the correlation time of magnetization τc. In this letter, we show that, for magnets with low-energy barriers (Δ ≈ kBT and below), circular disk magnets with in-plane magnetic anisotropy (IMA) lead to τc values that are two orders of magnitude smaller than τc of magnets with perpendicular magnetic anisotropy (PMA). Analytical descriptions demonstrate that this striking difference in τc is due to a precession like fluctuation mechanism that is enabled by the large demagnetization field in IMA magnets. We provide a detailed energy-delay performance evaluation of previously proposed BSN designs based on spin-orbit torque MRAM and spin-transfer torque MRAM employing low-barrier circular IMA magnets by SPICE simulations. The designs exhibit subnanosecond response times leading to energy requirements of approximately a few femtojoules to evaluate the BSN function, orders of magnitude lower than digital CMOS implementations with a much larger surface area. While modern MRAM technology is based on PMA magnets, results in this letter suggest that low-barrier circular IMA magnets may be more suitable for this application.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Spin–Orbit Torque-Controlled Magnetic Tunnel Junction With Low Thermal
           Stability for Tunable Random Number Generation
    • Authors: Vaibhav Ostwal;Joerg Appenzeller;
      Pages: 1 - 5
      Abstract: Spin-orbit torque has emerged as an alternative to spin-transfer torque switching of thermally stable magnetic tunnel junctions (MTJs). For MTJs with low thermal stability, i.e., low energy barrier MTJs, spin-orbit torque devices have been proposed, which allow for tunable random number generation and decoupled WRITE and READ paths. Such stochastic devices can then be interconnected to realize computational systems, such as Ising networks, neural networks, invertible logic, etc. In this letter, we experimentally demonstrate such a stochastic spin device called a “p-bit” that is characterized by a spin-orbit torque-controlled MTJ with low thermal stability as the WRITE unit, and where the tunneling magnetoresistance is employed as the READ unit. We first demonstrate deterministic switching of stable in-plane MTJs using the spin-orbit torques generated by tantalum. Next, we employ spin-orbit torques to tune the stochasticity of the MTJ with low thermal stability to generate tunable random numbers. National Institute of Standards and Technology randomness tests are performed to evaluate the quality of our random number generator. The results are then quantitatively analyzed using the standard model for thermally activated switching and the theory of thermal fluctuation in superparamagnetic particles. The devices presented in this letter consisting of a WRITE path (spin-orbit torque) and a READ path (MTJ) are the key building blocks for probabilistic spin logic applications.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Effects of Growth Order on Perpendicular Magnetic Anisotropy of
           Heavy-Metal/Ferromagnet/MgO Trilayered Structures
    • Authors: Yuejie Zhang;Xiaofei Yang;Peng Li;Jun Ouyang;Mingzhong Wu;
      Pages: 1 - 4
      Abstract: Previous experiments have shown that perpendicular magnetic anisotropy (PMA) in trilayers consisting of a CoFeB layer, an MgO layer, and a nonmagnetic metal (NM) layer depends strongly on whether the CoFeB layer was grown on the top of an NM layer or was capped by an NM layer. In this letter, we study the physical origin of this phenomenon through first-principles calculations. We took MgO/CoFe/Ta and Ta/CoFe/MgO as model structures and analyzed the magnetic anisotropy energy (MAE) therein. The “substrate/Ta/CoFe/MgO” structure had a notably higher MAE than the “substrate/MgO/CoFe/Ta” structure. This difference results mainly from different stresses in the Ta layers, and the latter gives rise to a difference in the hybridization strength of in-plane orbits (dxy, dx2-y2, px, and py). The p-orbital hybridization in the Ta layers contributes significantly to the PMA in both structures.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetic Radial Vortex Core and Coupled Edge-Soliton Pair Gyration
           Dynamics
    • Authors: Danna Dong;Cheng Li;Li Cai;Baojun Liu;Chuang Li;Jiahao Liu;Yabo Chen;
      Pages: 1 - 5
      Abstract: We studied the gyration dynamics of a magnetic radial vortex core by injecting spin-polarized current into a nanodisk through a nanocontact. The simulation results indicate that the radial vortex core can rotate in an approximately circular orbit with a stable frequency. As the current density increases, the radius and frequency of rotation increase, while the rotation stabilization time decreases. Simultaneously, the intensity of the interfacial Dzyaloshinskii–Moriya interaction has a great influence on the frequency and the maximum drive current density of the gyration. The Oersted field generated by the current can reduce the stabilization time. The radial vortex core transforms into an edge soliton pair and rotates stably along the boundary of the disk for a certain range of current densities. This work provides deeper insight into the gyration dynamics of magnetic radial vortices and the potential for the development of nano-oscillators based on radial vortices.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Reliable Five-Nanosecond Writing of Spin-Transfer Torque Magnetic
           Random-Access Memory
    • Authors: Guohan Hu;Janusz J. Nowak;Matthias G. Gottwald;Jonathan Z. Sun;Dimitri Houssameddine;Junghoon Bak;Stephen L. Brown;Pouya Hashemi;Qing He;Juhyun Kim;Chandrasekharan Kothandaraman;Gen Lauer;Hyun Koo Lee;Thitima Suwannasiri;Philip L. Trouilloud;Daniel C. Worledge;
      Pages: 1 - 4
      Abstract: We report reliable 5 ns switching of spin-transfer torque magnetoresistive random-access memory devices of nominal size 43 nm and a resistance area product of 11 Ω·μm2. We measured 256 devices with a 100% write-error-rate (WER) yield at a WER floor of 10-6 and a steep WER slope as a function of voltage. A single device had a WER less than 10-10 for 5 ns write pulses. We show promising 3 ns switching performance, with a 94% WER yield at a 10-6 WER floor, for 64 devices of nominal size 50 nm.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Low Energy Barrier Nanomagnet Design for Binary Stochastic Neurons: Design
           Challenges for Real Nanomagnets With Fabrication Defects
    • Authors: Md. Ahsanul Abeed;Supriyo Bandyopadhyay;
      Pages: 1 - 5
      Abstract: Much attention has been focused on the design of low energy barrier nanomagnets (LBMs), whose magnetizations vary randomly in time owing to thermal noise, for use in binary stochastic neurons (BSNs) that serve as hardware accelerators for machine learning. The performance of BSNs depends on two important parameters: the correlation time τc associated with the random magnetization dynamics in an LBM, and the spin-polarized pinning current Ip, which stabilizes the magnetization of an LBM in a chosen direction within a chosen time. We show that common fabrication defects in LBMs make these two parameters unpredictable because they are strongly sensitive to the defects. That makes the design of BSNs with real LBMs very challenging. Unless the LBMs are fabricated with extremely tight control, the BSNs that use them could be unreliable or suffer from poor yield.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Enhanced Thermal Stability in Magnetic Random-Access Memory Cells With
           Free Layer Composed of Multilayer Co/Pt Coupled to Co2Fe6B2 With
           Interfacial Perpendicular Magnetic Anisotropy
    • Authors: Jong-Ung Baek;Sun-Hwa Jung;Han-Sol Jun;Kei Ashiba;Jin-Young Choi;Jea-Gun Park;
      Pages: 1 - 5
      Abstract: A novel perpendicular spin-transfer torque magnetic random-access memory spin valve with a memory-cell size below 20 nm × 20 nm and a thermal stability factor Δ of ~77 (10-year retention time) was designed by ferromagnetically coupling a multiple free layer [Co/Pt]n to Co2Fe6B2 having interfacial perpendicular magnetic anisotropy (i-PMA) instead of coupling to a conventional double i-PMA free layer (Δ = 33). Thermal stability (Δ) increased with an increase of n in the [Co(0.47nm)/Pt(0.23 nm)]n multiple free layer. In particular, Δ = 80 could be achieved with n = 4 for a 15 nm × 15 nm memory-cell size. However, the tunneling magnetoresistance (TMR) ratio, which should be above 150% to assure a reasonable sensing margin, rapidly decreased from 190% to 98% with an increase in n from 0 to 4. This decrease was associated with W and Pt atomic diffusion into the MgO tunneling barrier. Improvement in the crystallinity of the MgO tunneling barrier increased the TMR ratio to 144% for n = 4.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • $_x$ Mn $_{100-}$ $_x$ /Co $_y$ Fe $_{100-}$ $_y$ +Films&rft.title=Magnetics+Letters,+IEEE&rft.issn=1949-307X&rft.date=2019&rft.volume=10&rft.spage=1&rft.epage=5&rft.aulast=Ando;&rft.aufirst=Sina&rft.au=Sina+Ranjbar;Masakiyo+Tsunoda;Muftah+Al-Mahdawi;Mikihiko+Oogane;Yasuo+Ando;">Compositional Dependence of Exchange Anisotropy in
           Pt $_x$ Mn $_{100-}$ $_x$ /Co $_y$ Fe $_{100-}$ $_y$ Films
    • Authors: Sina Ranjbar;Masakiyo Tsunoda;Muftah Al-Mahdawi;Mikihiko Oogane;Yasuo Ando;
      Pages: 1 - 5
      Abstract: Bilayer films consisting of a 15 nm thick PtxMn100-x(x = 48 or 15) layer and a 2 nm thick CoyFe100-y (0 ≤ y ≤ 90) layer were fabricated by ultrahigh-vacuum magnetron sputtering. The Pt48Mn52 and Pt15Mn85 films consisted of face-centered tetragonal (FCT) and face-centered cubic (FCC) structures, respectively. The effect of composition of CoFe films on the unidirectional anisotropy constant (Jk) in the PtxMn100-x /CoyFe100-y bilayer films and the optimum conditions for producing large Jk were determined. The FCT and FCC PtMn films annealed at 370 °C for 6 h both exhibited maximum Jk when the film composition was Co70Fe30. Blocking temperatures of the FCT and FCC PtMn films were 410 °C and 160 °C, respectively. All the bilayer films possess flat surfaces. These results indicate that the obtained Pt-Mn films-with low roughness, high exchange bias, and high blocking temperature-will be practical candidates as the antiferromagnetic layer in spintronic devices.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Dual-Bit Spin Dice Based on Spin–Orbit Torque in Perpendicular
           Magnetic Multilayers
    • Authors: Pinyun Yi;Haijiao Harsan Ma;Nuo Xu;Cheng Li;Binbin Yang;Liang Fang;Yue Hao;
      Pages: 1 - 5
      Abstract: In this letter, novel dual-bit spin dice based on spin-orbit torque are simulated. The design consists of two bistable magnetic tunnel junctions separated by a spacer layer of heavy metal. By utilizing the spin current at both sides of the heavy metal, the magnetization of free layers in the top and bottom magnetic tunnel junction can be pushed to a metastable state. Once the spin-orbit torque is removed, the magnetic moments of the two free layers relax to the stable state stochastically, which can be detected as two random numbers. A set of two random numbers is generated in a single device simultaneously, which leads to two-times improvement in the integration density and throughput over a conventional scenario. The simulation results indicate that the random bit streams can be produced steadily in the device against a wide range of process, voltage, and temperature variations. The designed system can generate random bits as fast as 200 MHz, while the energy consumption is only 18 fJ/bit, which has great potential in the fields of data/hardware security.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Interaction Between Thermal Magnons and Phonons in a CoFeB/Au
           Multilayer
    • Authors: Nandan K. P. Babu;Aleksandra Trzaskowska;Slawomir Mielcarek;Hubert Głowiński;Oleksandr M. Chumak;Milosz Zdunek;Jaroslaw W. Kłos;Maciej Krawczyk;
      Pages: 1 - 5
      Abstract: The dispersion relations of thermal magnons and phonons, which exist in a multilayered CoFeB/Au sample deposited on a silicon substrate, were determined by using Brillouin light scattering spectrometry in the oblique geometry, for the 45° angle between the in-plane-oriented static magnetization and the wave vector. Due to the low effective saturation magnetization of the multilayer, we were able to measure the crossing between the dispersion branches for spin waves and surface acoustic waves with the signature of the magnetoelastic interactions in the form of a coalescence of dispersion branches. The oblique geometry was chosen to enhance the interaction between both kinds of waves.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Soft Magnetism, Magnetostriction, and Microwave Properties of Fe-Ga-C
           Alloy Films
    • Authors: Xianfeng Liang;Cunzheng Dong;Sue J. Celestin;Xinjun Wang;Huaihao Chen;Katherine S. Ziemer;Michael Page;Michael E. McConney;John G. Jones;Brandon M. Howe;Nian X. Sun;
      Pages: 1 - 5
      Abstract: A systematic investigation of the soft magnetism, the change of modulus of elasticity with magnetization (ΔE effect), magnetostriction, and microwave properties has been carried out on iron-gallium-carbon thin films over a wide carbon content range. The phase transformation of the Fe-Ga-C films from bcc polycrystalline to amorphous leads to excellent magnetic softness with a low coercivity of less than 1 Oe, high saturation magnetization, narrow ferromagnetic resonance linewidth at 10 GHz of 20 to 30 Oe, and an ultra-low Gilbert damping constant of 0.0027. A record high piezomagnetic coefficient of 9.71 ppm/Oe, high saturation magnetostriction constant of 81.2 ppm, and large ΔE effect of -120 GPa at 500 nm were achieved.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Strong Coupling of Magnons to Microwave Photons in Three-Dimensional
           Printed Resonators
    • Authors: Vincent Castel;Sami Ben Ammar;Alexandre Manchec;Gwendal Cochet;Jamal Ben Youssef;
      Pages: 1 - 5
      Abstract: We report on ferromagnetic resonant mode hybridization in reentrant cavities made with a commercial three-dimensional (3-D) printer, followed by conventional 3-D metallization with copper and tin. The cavity volume was only 7% that of a standard cavity resonating at the same frequency while maintaining a high quality factor. Simulations were in very good agreement. We obtained an effective coupling of about 40 MHz in two cavities at room temperature. These experimental results demonstrate the utility of tunable filters based on complex 3-D printed cavities.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Effect of Dilute Rare-Earth Doping on Magnetodynamic Properties of
           Permalloy Films
    • Authors: Qian Chen;Yuli Yin;Honglei Yuan;Xiaochao Zhou;Zhaocong Huang;Jun Du;Ya Zhai;
      Pages: 1 - 5
      Abstract: Tunable magnetodynamic properties of magnetic materials will allow significant design freedom in spintronic devices. One of the most efficient methods to tailor magnetic properties is by element doping. Here, we study the effect of rare-earth (RE) doping on Permalloy (Py) films to modify the magnetic damping and exchange stiffness by both the ferromagnetic resonance uniform precession mode and the first perpendicular standing spin-wave mode. Results show that both static and dynamic magnetic properties of Py films are adjusted by doping with Gd, Tb, and Nd. The saturation magnetization is decreased by 59.4% with Tb, Gd, and Nd at concentrations of 10 at.%. The magnetic damping coefficient (α) is enhanced mostly by Tb dopant, followed by Nd and Gd, indicating that spin-orbit coupling may be one of the main mechanisms in determining α of RE-doped films. A 44.2% reduction of the exchange stiffness was achieved by doping with 3.3 at.% Nd. The results demonstrate that RE doping may be a viable technique for the control of magnetodynamic properties for spintronics applications.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • $_{25}$ Fe $_{75}$ +Films+Determined+by+Microfocused+Frequency-Resolved+Magneto-Optic+Kerr+Effect&rft.title=Magnetics+Letters,+IEEE&rft.issn=1949-307X&rft.date=2019&rft.volume=10&rft.spage=1&rft.epage=5&rft.aulast=Weiler;&rft.aufirst=Lukas&rft.au=Lukas+Liensberger;Luis+Flacke;David+Rogerson;Matthias+Althammer;Rudolf+Gross;Mathias+Weiler;">Spin-Wave Propagation in Metallic Co $_{25}$ Fe $_{75}$ Films Determined
           by Microfocused Frequency-Resolved Magneto-Optic Kerr Effect
    • Authors: Lukas Liensberger;Luis Flacke;David Rogerson;Matthias Althammer;Rudolf Gross;Mathias Weiler;
      Pages: 1 - 5
      Abstract: We investigated the magnetization dynamics of a patterned Co$_{25}$Fe$_{75}$-based heterostructure with a novel optical measurement technique that we call microfocused frequency-resolved magneto-optic Kerr effect. We measured the magnetic field dependence of the dynamical spin-wave susceptibility and recorded a spatial map of the spin waves excited by a microwave antenna. We compare these results to those obtained on the same sample with the established microfocused Brillouin light scattering technique. With both techniques, we find a spin-wave propagation length of 5.6 µm at 10 GHz. We also measured the dispersion of the wave vector and the spin-wave propagation length as a function of the external magnetic field. These results are in good agreement with the existing literature and with the Kalinikos–Slavin model.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Effect of Tantalum Spacer Thickness and Deposition Conditions on the
           Properties of MgO/CoFeB/Ta/CoFeB/MgO Free Layers
    • Authors: Thibaut Devolder;Sebastien Couet;Johan Swerts;Sofie Mertens;Siddharth Rao;Gouri Sankar Kar;
      Pages: 1 - 4
      Abstract: To get stable perpendicularly magnetized tunnel junctions at small device dimensions, composite free layers that comprise two MgO/FeCoB interfaces as sources of interface anisotropy are generally used. Proper crystallization and annealing stability are typically ensured by the insertion of a spacer layer of the early transition metal series within the FeCoB layer. We study the influence of the spacer thickness and growth condition on the switching metrics of tunnel junctions thermally annealed at 400 °C for the case of 1-4 Å Ta spacers. Thick Ta spacer results in large anisotropies indicative of a better defined top FeCoB/MgO interface, but this is achieved at the systematic expense of stronger damping. For the best anisotropy-damping compromise, junctions of diameter 22 nm can still be stable and spin-torque switched. Coercivity and inhomogeneous linewidth broadening, likely arising from roughness at the FeCoB/Ta interface, can be reduced if a sacrificial Mg layer is inserted before the Ta spacer deposition.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnon Straintronics to Control Spin-Wave Computation: Strain
           Reconfigurable Magnonic-Crystal Directional Coupler
    • Authors: Alexandr V. Sadovnikov;Andrey A. Grachev;Alexey A. Serdobintsev;Svetlana Evgenevna Sheshukova;Sergey S. Yankin;Sergey A. Nikitov;
      Pages: 1 - 5
      Abstract: The effect of electrical field control of the spin-wave spectrum in adjacent magnonic crystals stripes was investigated by micromagnetic simulation, microwave spectroscopy, and Brillouin light scattering (BLS). The electric-field-induced dipolar coupling between magnetic stripes leads to the formation of symmetric and antisymmetric collective modes in the spectra of propagating spin waves. In particular, the strain-induced variation of the spin-wave coupling length in the stripe, predicted by micromagnetic simulation and measured by BLS, show the possibility of application of a lateral array of magnonic crystals as tunable microwave directional couplers, power dividers, and spin-wave demultiplexers, which can be used simultaneously as an interconnection unit in reconfigurable magnonic networks.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Nonlinear Spin-Wave Logic Gates
    • Authors: Alexey B. Ustinov;Erkki Lähderanta;Mitsuteru Inoue;Boris A. Kalinikos;
      Pages: 1 - 4
      Abstract: A nonlinear spin-wave (magnonic) logic gate based on the ferrite-film Mach-Zehnder interferometer was realized. The gate has two inputs and one output. The principle of operation of the device is based on the power-dependent phase shift of spin waves propagating in an yttrium iron garnet film. A xor logic functionality for two digital data streams supplied to the gate inputs is shown. No control signal is needed for the gate operation. The performance characteristics of the device are discussed. Reliable functionality in the pulsed regime at 50 and 250 kb/s is demonstrated.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Simultaneous Control of Interlayer Exchange Coupling and the Interfacial
           Dzyaloshinskii–Moriya Interaction in Ru-Based Synthetic Antiferromagnets
           
    • Authors: Aleksandr Prudnikov;Maxwell Li;Marc De Graef;Vincent Sokalski;
      Pages: 1 - 4
      Abstract: We present a Ru-based synthetic antiferromagnet (SAF) made with asymmetric ferromagnetic building blocks (Pt/Co/Ir or Ir/Co/Pt) to couple their interfacial Dzyaloshinskii-Moriya interaction (DMI) with strong interlayer exchange coupling (IEC). This combination may lead to new types of antiferromagnetic domain walls (DWs), which are conceptually presented in this letter. These include an energetically frustrated configuration and an “isolated” spin chain where a net magnetization exists only at the DW. While most SAF designs incorporate a Co/Ru/Co IEC layer, chiral SAFs require Pt and/or Ir at the Ru/Co interface. In all cases except Pt/Ru/Pt, a significant IEC field is preserved over a range of Ru thicknesses, with the largest occurring for Ir/Ru/Ir. These results demonstrate that ferromagnetic film stacks with purportedly strong DMI can be incorporated into SAFs without compromising IEC.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Laser-Reduced Zeolite Imidazole Framework-67 as Magnetic Absorbents for
           Oil Separation in Water
    • Authors: Junfeng Huang;Kam Chuen Yung;Guijun Li;Zhuoxun Wei;Zhengong Meng;
      Pages: 1 - 3
      Abstract: We reduced zeolite imidazole framework-67 by laser so as to prepare porous carbon materials embedded with cobalt nanoparticles. The composites exhibited ferromagnetic behavior. The parameters of laser reduction were optimized for oil absorption with high capacity and good reusability. This approach can open a new class of ferromagnetic porous absorbents and represent advancement toward overcoming the limitations of oil absorption.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Multistate Nanomagnetic Logic Using Equilateral Permalloy Triangles
    • Authors: Meshal Alawein;Selma Amara;Hossein Fariborzi;
      Pages: 1 - 5
      Abstract: We examine a multistate logic computation scheme based on nanomagnets with configurational anisotropy (CA). We present a case study of a structure comprising a thin equilateral triangle-exhibiting sixfold CA-and three surrounding bistable inputs/outputs, where all nanomagnets generally can be interconnected by nanomagnetic chains and adiabatically clocked by external magnetic fields. We analyze the design and operation of the triangle with three-dimensional micromagnetic simulations of the magnetization configurations and dynamics, the effect of thermal fluctuations, and the propagation of information to an output nanomagnet. As a proof of concept, we demonstrate reconfigurable NAND/NOR and OR/AND gates as potential logic applications. We highlight further applications and suggest directions for future research.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Peak in Angular Dependence of Coercivity in a Hexagonal Array of Permalloy
           Spherical Nanocaps
    • Authors: Yuset Guerra Davila;Frederico Alves Revoredo Júnior;Ramon Peña-Garcia;Eduardo Padrón-Hernández;
      Pages: 1 - 3
      Abstract: Micromagnetic simulations of coercivity as a function of external magnetic field direction were performed for a hexagonal array of hemispherical Permalloy nanocaps. The analysis was based on hysteresis loops for arrangements of nanocaps of variable thickness (5 nm and 10 nm). The angular dependence of coercivity had a maximum at about 80° with respect to the arrangement plane. An increase in coercivity with nanocap thickness is related to the magnetization reversal mechanism, where the dipole energy of individual caps generates an effective intermediate axis, locking the magnetic moments. The coercivity has maximum values of 109 Oe for 5 nm and 156 Oe for 10 nm thickness. The remanence decreases monotonically with angle. This is associated with the influence of shape anisotropy, where the demagnetizing field in the plane of the array is much smaller than the demagnetizing field perpendicular to the plane.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Double-Vortex-Assisted Asymmetric Magnetoreactance in H-Shaped Nanomagnets
    • Authors: Andrzej Janutka;Kacper Brzuszek;
      Pages: 1 - 5
      Abstract: We model the dynamical response of H-shaped layered nanostructures to the alternating current carried in a nonmagnetic substrate, which induces an alternating Oersted field inside the magnetic layer, in the presence of a static field transverse to the current-flow direction. The current is directed horizontally, whereas the field is vertical with respect to the H-letter shape of the structure. Reversal of the field induces a highly asymmetric transverse magnetoreactance in the magnetically soft nanomagnet due to the structure's double magnetic vortex. Micromagnetic simulations, for a specific resonant frequency of the alternating current, show the reactance change by over 100% in the vicinity of zero field, with a relatively large sensitivity to the magnetic field. The mechanism for the dynamical response of the nanomagnet is related to oscillations in the separation of the vortex cores.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Nonlinear Ferromagnetic Resonance in the Presence of Three-Magnon
           Scattering in Magnetic Nanostructures
    • Authors: Denys V. Slobodianiuk;Gennadiy A. Melkov;Katrin Schultheiss;Helmut Schultheiss;Roman V. Verba;
      Pages: 1 - 5
      Abstract: Bulk and patterned ferromagnets can exhibit various nonlinear phenomena at moderate excitation power, making them a nice test bed for study of nonlinear dynamics. We investigate nonlinear ferromagnetic resonance in magnetic nanostructures with discrete spectra of spin-wave modes in the case of allowed three-magnon scattering processes. These processes result in the splitting of a directly driven spin-wave mode into two secondary modes, if a certain excitation threshold is overcome. The three-magnon splitting manifests itself as a characteristic distortion of the resonance curve, which can be detected in a simple ferromagnetic resonance experiment. Theoretical results are also compared to the experimental study of nonlinear spin-wave dynamics in a vortex-state magnetic disk, in which three-magnon splitting is confirmed by direct measurements using Brillouin light-scattering microscopy.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Alignment Optimization of the Dielectrophoresis of Ni Nanowires Through
           External Magnetic Field
    • Authors: Bruno Luís Segat Frare;Marcos Vinícius Puydinger dos Santos;Fanny Béron;
      Pages: 1 - 5
      Abstract: Nanowires are increasingly being used in sensor devices because they are highly sensitive to the environment. Industrial applications take advantage of their shape anisotropy, high aspect ratio, and electronic transport characteristics. The fabrication and characterization of nanowire-based devices require proper control during their deposition, which currently represents a major challenge. Dielectrophoresis (DEP) is a useful technique for nanowire deposition, although it does not guarantee their precise alignment, which must be treated stochastically. In this letter, we combined DEP with an external magnetic field up to 80 kA/m to improve alignment control over Ni nanowires (4 μm length and 35 nm diameter) during deposition on Pt electrodes. Statistical analysis suggests that the nanowires tend to align along the magnetic field axis. In addition, DEP showed a considerable influence in trapping nanowires at the electrodes because the DEP torque is the greatest in this region, whereas the torque due to the magnetic field is predominant at distances above 10 μm from the electrodes. Our results can be employed to further investigate the electrical transport properties of nanowires of different materials, as well as for fabricating nanowire-based devices, such as field-effect transistors and nanoelectromechanical system platforms.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Unexpected Development of Perpendicular Magnetic Anisotropy in Ni/NiO
           Multilayers After Mild Thermal Annealing
    • Authors: Dimitrios I. Anyfantis;Eirini Sarigiannidou;Laetitia Rapenne;Alkeos Stamatelatos;Dimitrios Ntemogiannis;Vassilios Kapaklis;Panagiotis Poulopoulos;
      Pages: 1 - 5
      Abstract: We report on the significant enhancement of perpendicular magnetic anisotropy of Ni/NiO multilayers after mild annealing up to 90 min at 250 °C. Transmission electron microscopy shows that after annealing, a partial crystallization of the initially amorphous NiO layers occurs. This turns out to be the source of the anisotropy enhancement. Magnetic measurements reveal that even multilayers with Ni layers as thick as 7 nm, which in the as-deposited state showed inplane anisotropy with square hysteresis loops, show reduced in-plane remanence after thermal treatment. Hysteresis loops recorded with the field in the normal-to-film-plane direction provide evidence for perpendicular magnetic anisotropy with up and down magnetic domains at remanence. A plot of effective uniaxial magnetic anisotropy constant times individual Ni layer thickness as a function of individual Ni layer thickness shows a large change in the slope of the data attributed to a drastic change of volume anisotropy. Surface anisotropy showed a small decrease because of some layer roughening introduced by annealing.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Bulk-Like Dynamic Magnetic Properties of Nickel Ferrite Epitaxial Thin
           Films Grown on SrTiO3(001) Substrates
    • Authors: Viktor E. Bursian;Andrey K. Kaveev;Alexander M. Korovin;Boris B. Krichevtsov;Leonid V. Lutsev;Sergey M. Suturin;Masahiro Sawada;Nikolai S. Sokolov;
      Pages: 1 - 5
      Abstract: Nickel ferrite (NiFe2O4, NFO) films were grown at high temperatures on SrTiO3(001) substrates using laser molecular beam epitaxy. A spinel lattice structure, with lattice parameters close to those of bulk NFO, was confirmed by electron and X-ray diffraction. Vibrating sample magnetometer measurements show an in-plane remanent magnetization, relatively narrow (~50 Oe) hysteresis loops, and fourfold symmetry. Soft X-ray magnetic dichroism measurements indicate an inverse spinel structure. X-band ferromagnetic resonance (FMR) measurements show a line width as low as 45-50 Oe, which corresponds to the value for bulk NFO crystals. The angular dependence of FMR on a 110 nm thick NFO film indicates cubic anisotropy close to that of bulk crystals and a substrate-induced stress anisotropy field of about 0.4 kG.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Anisotropy of Assemblies of Densely Packed Co-Alloy Nanoparticles Embedded
           in Carbon Nanotubes
    • Authors: Serghej L. Prischepa;Alexander L. Danilyuk;Andrei V. Kukharev;Costel S. Cojocaru;Nikolai I. Kargin;Francois Le Normand;
      Pages: 1 - 5
      Abstract: We report on the magnetic properties of an array of binary metal CoFe, CoNi, and CoPt nanoparticles (NPs) embedded inside vertically oriented carbon nanotubes (CNTs). Samples were synthesized by chemical vapor deposition activated by current discharge plasma and hot filaments. Assemblies of Co-based catalytic NPs were prepared on SiO2/Si substrates by sputtering ultrathin films followed by reduction in an H2/NH3 mixture. As a result of the CNT growth, each CNT contained only one ferromagnetic NP located at the top. For all samples, the easy axis of magnetization was along the CNT axis. The magnetic parameters, including effective anisotropy constant and the contributions of dipole interactions and shape, magnetocrystalline, and magnetoelastic anisotropies, were estimated based on the experimental data and a random-anisotropy model. The magnetoelastic contribution was decisive. From the magnetoelasticity, the stresses in the NPs embedded in the CNTs were determined. Finally, the magnetization distribution in CoFe, CoNi, and CoPt NPs was simulated considering the magnetoelastic contribution.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Synthesis and Characterization of Fe–Co–V High-Magnetization
           Nanoparticles Obtained by Physical Routes
    • Authors: Virginia Vadillo;Jon Gutiérrez;Maite Insausti;Joseba S. Garitaonandia;Izaskun Gil de Muro;Iban Quintana;Jose Manuel Barandiarán;
      Pages: 1 - 5
      Abstract: We present results of the synthesis and characterization of Fe-Co-V high-magnetization ferromagnetic nanoparticles (NPs) fabricated by two physical routes: laser ablation in liquid flow and mechanical ball milling. As characterizing techniques, we used dynamic light scattering, X-ray diffraction, transmission and scanning electron microscopy, and magnetic measurements. The starting material was Fe49Co49V2 (bulk Vacoflux 50 from Vacuumschmelze), a soft magnetic alloy with a high saturation magnetization of about 2.3 T or 220 emu/g. Using a picosecond pulsed laser at λ = 355 and 532 nm with flowing liquid acetone, we obtained NPs about 10-50 nm in size, with saturation magnetization of 3 memu/ml. By employing high-energy ball milling (24 h total milling time), we obtained NPs that are about 0.5-1 μm in size, with bcc structure and about 195 emu/g saturation magnetization. All these results indicate that the main differences between the two fabrication methods are the final quantity and morphology of the NPs.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Chemical Synthesis of Cobalt Nanochains
    • Authors: Akhilesh Kumar Srivastava;Raju V. Ramanujan;
      Pages: 1 - 5
      Abstract: Cobalt nanochains of elongated and equiaxed nanoparticles were made by a simple and facile thermal decomposition of chemically synthesized cobalt oxalate nanorods. Such magnetic chains are relevant to high-density data storage applications. The kinetics of chain formation from the rods were in reasonable agreement with the Rayleigh criterion, when the additional factor of magnetostatic interaction was taken into account. The rods were transformed into chains by the ovulation mechanism proposed by Nichols. Both hexagonal close-packed and face-centered cubic phases were obtained in the chains. The Co nanochains exhibited enhanced coercivity compared to bulk Co or randomly dispersed nanoparticles. The magnetic coercivity of the chains of elongated nanoparticles was greater than the coercivity of chains of equiaxed nanoparticles due to shape anisotropy. A similar approach may be used to produce nanostructures of other metal and metal oxide materials for applications, such as bioengineering, catalysis, and imaging.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Negative Thermal Expansion in Nanostructured Intermediate-Valence
           YbAl3
    • Authors: Cristina Echevarria-Bonet;Maria de la Fuente Rodriguez;Jose I. Espeso;Jesus Angel Blanco Rodriguez;Inés Puente Orench;Daniel P. Rojas;Lidia Rodríguez Fernández;Francois Fauth;Luis Fernández Barquín;
      Pages: 1 - 5
      Abstract: Interest in the strongly correlated electron system YbAl3 has been recently renewed by the observation of a breakdown of coherence effects and Fermi liquid behavior when the alloy's particle size is reduced to around 11 nm. Powder diffraction measurements using neutron and synchrotron radiation allow us to estimate the thermal expansion of the nanostructured YbAl3. A region of negative thermal expansion in the nanostructured material occurs at higher temperatures compared to that of bulk YbAl3. This shows that the reduction in the size of YbAl3 not only affects electronic properties, but also the lattice dynamics of this material.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Tuning of Exchange-Biased Ni-Mn/Fe-Ni Films With High Blocking
           Temperatures
    • Authors: Mikhail E. Moskalev;Egor V. Kudyukov;Vladimir N. Lepalovskij;Vladimir O. Vas'kovskiy;
      Pages: 1 - 5
      Abstract: Effect of a reduction in an antiferromagnetic layers' thickness and insertion of a Ta spacer on thermal behavior of exchange bias field, coercivity, and on blocking temperature of Ni-Mn-based exchange-biased films is studied. Reduction of a Ni-Mn layer's thickness from 20 to 17.5 nm to 14 and 12 nm gradually decreases the exchange bias field. The dependence of the blocking temperature on the thickness of a Ni-Mn layer shows a finite-size scaling effect with a maximum blocking temperature of 650 K for a 20 nm thick antiferromagnetic layer. Despite that, an unusually stable or even increasing exchange bias is present for some thicknesses in the temperature range up to 400 K. Addition of a Fe-Ni buffer with an increase in Ni concentration in Ni-Mn layer yields a greater exchange-bias-field-to-coercivity ratio and an even better thermal stability of exchange bias, which remains steady in the range from 300 to 475 K. Addition of a very thin Ta spacer (0.1 nm, 0.2 nm, or 0.3 nm thick) significantly decreases the exchange bias field, while only slightly decreasing the blocking temperature. A peak in the coercivity at around 700 K is found for all of the studied films, and is likely due to structural transformations.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetostructural Phase Transition in Micro- and Nanosize
           Ni–Mn–Ga–Cu Alloys
    • Authors: Alexey V. Mashirov;Artemy V. Irzhak;Nataliya Yu. Tabachkova;Filipp O. Milovich;Alexander P. Kamantev;Dewei Zhao;Jian Liu;Valeria G. Kolesnikova;Valeria V. Rodionova;Victor V. Koledov;
      Pages: 1 - 4
      Abstract: The characteristic temperatures of the magnetostructural phase transition in lamella of the Heusler alloy Ni50Mn18.5Ga25Cu6.5 increase with decreasing geometric dimensions to nanometers. The martensite phase was detected in the nanoscale portion at temperatures above Ms = 309 K by transmission electron microscopy, whereas only the austenite phase existed in the microsize part of the sample. The shift of the characteristic temperatures with decreasing sizes of samples must be taken into account when creating microelectromechanical systems based on Heusler alloys.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Thermal Treatment of Chains of Amorphous Fe1–x Co x Nanoparticles Made
           by Magnetic-Field-Induced Coreduction Reaction
    • Authors: Marcin Krajewski;Mateusz Tokarczyk;Tomasz Stefaniuk;Sabina Lewińska;Anna Ślawska-Waniewska;
      Pages: 1 - 5
      Abstract: For the first time this work presents the studies on the thermal treatment of amorphous nanochains composed of ${rm{Fe_{1-x}CO_{x}}}$ nanoparticles. Such nanostructures were manufactured applying the magnetic-field-induced co-reduction reaction, in which the precursor solutions containing 1:3 and 3:1 proportions of ${rm{Fe^{2+}}}$ and ${rm{CO^{2+}}}$ ions were reduced with sodium borohydride. Afterwards, the as-prepared nanochains were heated for 30 min at 400 °C and 500 °C in two atmospheres containing different amount of oxygen. This process led to their oxidation and, as a result, the thermally treated Fe-Co nanochains were mainly transformed into cobalt ferrite. Moreover, it is proven that the heating at 500 °C in the air-containing atmosphere leads to losing the nanochain structure. According to the room temperature magnetic measurements, the as-prepared and thermally treated Fe-Co nanochains were ferromagnetic materials. The highest saturation magnetization (${M_{s}}$) was recorded for the ${rm{Fe_{1-x}CO_{x}}}$ nanochains treated at 400 °C in dry air (105 A${cdotrm{M^{2}/Kg}}$ and 154 A${cdotrm{M^{2}/Kg}}$ for ${rm{Fe_{0.25}CO_{0.75}}}$ and ${rm{Fe_{0.75}CO_{0.25}}}$, respectively), whereas the lowest ${M_{s}}$ was found for the ${rm{Fe_{0.25}CO_{0.75}}}$ heated at 500 °C in dry air (17 A${cdotrm{M^{2}/Kg}}$) and the ${rm{Fe_{0.25}CO_{0.75}}}$ heated at 500 °C in argon (16 A${cdotrm{M^{2}/Kg}}$).
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Ground-State Magnetic Phase in Transition-Metal-Doped Boron Nitride
           Nanosheet With (5,0) Chirality
    • Authors: Akram Malek;Tayebeh Movlarooy;Saeid Hessami Pilehrood;
      Pages: 1 - 4
      Abstract: The ground-state magnetic coupling in a (5,0) armchair BN nanosheet doped with dual 3d transition metals was studied using first-principles calculations for three different configurations. When substituting two B atoms, the relative energies of the states between ferromagnetic (FM) and antiferromagnetic (AFM) coupling are investigated. Energy differences between FM and AFM states suggest that the preferable magnetic state for the BN nanosheet doped with a pair of Fe atoms independent of doping site is AFM, whereas for the Cr-, Mn-, and Co-doped BN nanosheet, the magnetic state changes as the transition metals configuration varies. In order to identify the most stable configuration, the formation energy is calculated for all compounds. The formation energy calculations identify a particular stable configuration for doping with pairs of Co, Fe, Mn, or Cr atoms. Of these, the Co-doped BN nanosheet has the most stable structure.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Signal Detection Under Multipath Intersymbol Interference in Staggered
           Bit-Patterned Media Recording Systems
    • Authors: Seongkwon Jeong;Jaejin Lee;
      Pages: 1 - 5
      Abstract: Bit-patterned media recording was invented with the aim of achieving high areal density. However, bit-patterned media recording suffers from two-dimensional (2-D) interference problems, including intersymbol interference in the down-track direction and intertrack interference in the cross-track direction. The 2-D interference corrupts the readback signal and degrades the performance of bit-patterned media recording. Unlike the layout of regular-array bit-patterned media, in the layout of staggered-array bit-patterned media, islands along neighboring tracks are displaced by a half-period from islands on the main data track; hence, in terms of intertrack interference, the islands on the main data track are predominantly affected by the closest four islands on neighboring tracks. To address this problem, a proper signal detection scheme for staggered bit-patterned media recording should be developed. In this letter, we introduce a multipath soft-output Viterbi algorithm for reducing the 2-D interference in staggered bit-patterned media recording. We investigate different partial response targets and compare the performances of the one-dimensional, two-dimensional, and proposed three-path soft-output Viterbi algorithm.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Impact of Magnetic Medium Grain Height in Heat-Assisted Magnetic Recording
    • Authors: Yuwei Qin;Jian-Gang Zhu;
      Pages: 1 - 5
      Abstract: Compared to conventional perpendicular magnetic recording, heat-assisted magnetic recording occurs at temperatures more than twice as high in degrees Kelvin. The ability of head field to align the medium magnetization over the short duration in recording a bit is limited by the ratio of magnetic potential energy to the thermal energy. In this letter, we present a systematic micromagnetic modeling study of the transition jitter resulting from thermal agitation during the recording process. As we continue to decrease grain size in order to increase recording areal density, the height of grains in the recording medium needs to increase accordingly to keep the number of magnetization-misaligned grains to a minimum.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Improvement in Bit Error Rate With a Combination of a Rate-3/4 Modulation
           Code
           
    • Authors: Chaiwat Buajong;Chanon Warisarn;
      Pages: 1 - 5
      Abstract: To improve the bit-error-rate (BER) performance of an ultrahigh-density bit-patterned magnetic recording (BPMR) system, the intersymbol interference and intertrack interference (ITI) effects resulting from the reduction of spacing between bit islands in both along-track and across-track directions must be efficiently handled. Array-reader-based BPMR is considered a key technology for future magnetic recording due to its advantages, such as its diversity gain against noise and ITI cancellation. This letter proposes a three-reader, four-track system where a simple rate-3/4 two-dimensional (2-D) modulation code and a new ITI subtraction technique are used to improve recording system performance. Moreover, a 2-D Viterbi detector is modified in accordance with the ITI subtraction scheme, which leads to lower complexity and better BER performance. Simulations demonstrate improvement in performance gains under position and size fluctuation effects.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • An Efficient Syndrome Calculator for Varshamov–Tenengolts Codes in
           Vertical Racetrack Memory
    • Authors: Tayyeb Mahmood;Ubaid Ullah Fayyaz;Ata-ur-Rehman Makhdoom;
      Pages: 1 - 5
      Abstract: Spintronic racetrack memory stores binary information in magnetic domains, isolated with domain walls and movable within a nanowire. Because the domain wall motion is probabilistic, Varshamov–Tenengolts (VT) codes have been applied to such devices due to their ability to correct single-bit deletion and insertion. The complexity of the VT encoder and decoder is largely because of a sequential syndrome calculator that employs modulo-additions. Previous implementations avoided this complexity by restricting the racetrack size to a specific number of magnetic domains. In this letter, we describe an efficient implementation of the syndrome calculator with a novel steering algorithm, which not only alleviates the above-mentioned restrictions but also reduces adder size and the required number of operations, exploiting modulo-arithmetic symmetries in VT codes. We synthesize the syndrome calculator with varying number of domains to show that the algorithm is scalable, increases areal efficiency, slashes processing time, and lowers the power consumption of a VT encoder and decoder.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetic Loss Decomposition in Co-Doped Mn-Zn Ferrites
    • Authors: Samuel Dobák;Cinzia Beatrice;Fausto Fiorillo;Vasiliki Tsakaloudi;Carlo Ragusa;
      Pages: 1 - 5
      Abstract: The magnetic properties of sintered Mn-Zn ferrites, Co2+ enriched by addition of CoO up to 6000 ppm, were measured in ring samples for a broad range of peak polarization values (2-200 mT) and frequencies (dc - 1 GHz). The results were analyzed by separating the contributions to the magnetization process of domain wall motion and magnetization rotation, and applying the concept of loss decomposition. By determining the value and behavior of the rotational permeability μrot as a function of the CoO content, we obtain the average effective magnetic anisotropy and its effect on the loss. We thus identify the hysteresis (quasi-static) Wh, rotational Wrot, and excess Wexc loss components and their dependence on CoO. The quasi-static loss Wh, the domain wall permeability μdw, and have minima, and μrot has a maximum, for CoO in the range 3000-4000 ppm. The rotational loss by spin damping Wrot,sd is calculated by use of the Landau-Lifshitz equation by assuming distributed anisotropy field amplitudes. Wrot,sd covers the experimental loss behavior beyond about 1 MHz. Wexc and Wh, both directly generated by the moving domain walls, share the dissipative response of the material at lower frequencies and show similar trends versus CoO content. It is concluded that the modulation of the magnetic anisotropy of Mn-Zn ferrites through Co2+ enrichment, leading to maximum magnetic softening for CoO in the range 3000-4000 ppm, can be assessed in terms of separate effects of domain wall motion and moment rotations and their related dissipative properties.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Magnetic Thin-Film Inductors With Induced Radial Anisotropy for Improved
           Inductance Density
    • Authors: Michael S. Lekas;Ryan Davies;Noah Sturcken;
      Pages: 1 - 4
      Abstract: This letter presents the design and electrical performance of integrated power inductors based on thin-film magnetic cores with radial anisotropy induced by in situ magnetic annealing. The magnetic anneal uses an additional coil, as part of the CMOS interconnect below the core, to simultaneously apply a biasing magnetic field and act as a resistive heater. Following annealing, devices demonstrated inductance enhancements as high as 8.8 times the original as-fabricated value, a peak inductance-to-dc resistance $(L/R_{{rm{dc}}})$ of 348 nH/Ω, a peak volumetric inductance density of 935 nH/mm3, and a peak areal inductance density of 33.4 nH/mm2. Additional improvements in inductor and bias coil design should further improve device $L/ R_{{rm{dc}}}$ ratios to greater than 450 nH/Ω.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • $_{x}$ N+Metallic+Glass+Composites+Fabricated+by+Spark+Plasma+Sintering&rft.title=Magnetics+Letters,+IEEE&rft.issn=1949-307X&rft.date=2019&rft.volume=10&rft.spage=1&rft.epage=5&rft.aulast=Lavernia;&rft.aufirst=Todd&rft.au=Todd+C.+Monson;Baolong+Zheng;Robert+E.+Delany;Charles+J.+Pearce;Eric+D.+Langlois;Stefan+M.+Lepkowski;Tyler+E.+Stevens;Yizhang+Zhou;Stanley+Atcitty;Enrique+J.+Lavernia;">Soft Magnetic Multilayered FeSiCrB–Fe $_{x}$ N Metallic Glass Composites
           Fabricated by Spark Plasma Sintering
    • Authors: Todd C. Monson;Baolong Zheng;Robert E. Delany;Charles J. Pearce;Eric D. Langlois;Stefan M. Lepkowski;Tyler E. Stevens;Yizhang Zhou;Stanley Atcitty;Enrique J. Lavernia;
      Pages: 1 - 5
      Abstract: Novel multilayered FeSiCrB-FexN (1 = 2-4) metallic glass composites were fabricated using spark plasma sintering of FeSiCrB amorphous ribbons (Metglas 2605SA3 alloy) and FexN (1 = 2-4) powder. Crystalline FexN can serve as a high magnetic moment, high electrical resistance binder, and lamination material in the consolidation of amorphous and nanocrystalline ribbons, mitigating eddy currents while boosting magnetic performance and stacking factor in both wound and stacked soft magnetic cores. Stacking factors of nearly 100% can be achieved in an amorphous ribbon/iron nitride composite. FeSiCrB-FexN multilayered metallic glass composites prepared by spark plasma sintering have the potential to serve as a next-generation soft magnetic material in power electronics and electrical machines.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Nanostructured Zn-Substituted Nickel Ferrite Thin Films: CMOS-Compatible
           Deposition and Excellent Soft Magnetic Properties
    • Authors: RD Ralandinliu Kahmei;Ranajit Sai;Sarath Arackal;S.A. Shivashankar;Navakanta Bhat;
      Pages: 1 - 5
      Abstract: Nanostructured NixZn1-xFe2O4 (x = 1, 0.5) films, about 1.5 μm thick on Si (100) substrates, were deposited using a low-temperature ('150 °C) microwave-assisted solvothermal (MAS) technique that is compatible with back-endof-the-line Si-CMOS processing. A nanocrystalline single-phase spinel structure with crystallite sizes of ~4 nm for the nickel ferrite film (NF) and ~6 nm for the zinc-substituted NF (ZNF) was obtained. The films demonstrate excellent surface smoothness and strong adherence to the substrate. Deconvolution of the A1g vibration mode in Raman spectra of both films reveals a “far-from-equilibrium” crystallographic inversion induced by the MAS process. Its effect on the magnetic characteristics of the films is analyzed here. Both films exhibit in-plane (xy plane) isotropy with very low room-temperature coercivities, 25 Oe for NF and 35 Oe for ZNF, which is essential for high-frequency, soft magnetic applications. The presence of interparticular dipolar interaction in both films is confirmed from temperature-dependent magnetization measurements made under different dc bias fields. The CMOS-compatible ferrite processing and superparamagnetic Ni-ferrite and NiZn-ferrite thin films presented here can meet upcoming technological needs in on-chip integrated passive devices.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Dy Electrodeposition on Sintered Nd-Fe-B
    • Authors: Runmiao Wang;Aizhi Sun;Huizhen Lang;Xiaotian Tang;
      Pages: 1 - 5
      Abstract: A low-cost, high-efficiency electrodeposition technique was used to enhance the coercivity of Nd-Fe-B. Dy was electrodeposited on the surface of a sintered Nd-Fe-B magnet in a nonaqueous solution. The use of the organic solvent dimethylformamide results in improved electrodeposition and adhesion compared to ethanol. A dense deposition layer was achieved when current density was
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • High-Sensitivity Three-Axis Vector Magnetometry Using Electron Spin
           Ensembles in Single-Crystal Diamond
    • Authors: Binbin Zhao;Hao Guo;Rui Zhao;Fangfang Du;Zhonghao Li;Lei Wang;Dajin Wu;Yulei Chen;Jun Tang;Jun Liu;
      Pages: 1 - 4
      Abstract: We demonstrate a three-axis vector magnetometer based on ensembles of negatively charged nitrogen vacancy centers in single-crystal diamond. A diamond with C3v symmetry was used to establish the coordinate system for vector magnetic field sensing. We control the external static magnetic field with three-axis Helmholtz coils. Four pairs of magnetic resonance peaks were obtained, which were used to calculate the three Cartesian components of the magnetic field with sensitivity of ~ 5 nT √Hz for each Cartesian component, free of interaxis error. The magnetometer is suitable for single-chip manufacturing.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Ferromagnetic Object Localization Based on Improved Triangulating and
           Ranging
    • Authors: Zhicheng Yang;Shenggang Yan;Lianping Chen;Bin Li;
      Pages: 1 - 5
      Abstract: The performance of scalar triangulation and ranging (STAR) for the localization of ferromagnetic objects is limited by asphericity error. Alternatively, iterative strategies may be used to reduce error and improve performance. However, iterative methods have problems, such as multiple required iterations, singularities, and limited accuracy. Eigenvalue methods are primarily based on the property of gradient tensor eigenvalues. A rotationally invariant scalar related to eigenvalues can eliminate the asphericity error. Additionally, a new strategy for estimating the length of the bearing vector is simpler and can be used to avoid singularities. With these two improvements, the formula for estimating the bearing vector is more concise and direct. The results show that the eigenvalue method performs better than the STAR and iterative methods.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Demagnetizing Field Caused by Specimen End Gaps in Electromagnet
           Measurements of Permanent Magnet Materials
    • Authors: Du-Xing Chen;
      Pages: 1 - 4
      Abstract: The midplane and volume-averaged demagnetizing factors, Nmid and Nvol, for a uniformly magnetized cylinder of length ls and radius rs clamped in the pole gap of an electromagnet with end gaps of total length ds are calculated as functions of ds/ls and ls/(2rs) and used for converting the measured magnetization-field curves of an Alnico specimen for different values of ds. The maximum ds/ls allowed for permanent magnet measurements stated in IEC and ASTM standards are discussed.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Compact Magnetic Field Sensor Based on a Magnetic-Fluid-Integrated Fiber
           Interferometer
    • Authors: Wenwen Wu;Ye Cao;Hao Zhang;Bo Liu;Xu Zhang;Shaoxiang Duan;Yange Liu;
      Pages: 1 - 5
      Abstract: A compact, low-cost, fiber-compatible magnetic field sensor based on multimodal interference in an S-taper and up-fusion-taper fiber modal interferometer is designed and experimentally demonstrated. The spectral characteristics in response to applied magnetic field and environmental temperature have been analyzed in detail. Experimental results indicate that the magnetic sensitivity reaches -0.03464 nm/Oe for a magnetic field ranging from 40 to 160 Oe. The proposed sensor has a maximum temperature sensitivity of 0.04889 nm/°C when the temperature increases from 27 to 45 °C. The effect of temperature on wavelength shift could be resolved by using a matrix containing the magnetic field and temperature sensitivities for two selected interferometric dips.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Calibration of Magnetometer Arrays in Magnetic Field Gradients
    • Authors: Yaxin Mu;Xiaojuan Zhang;Wupeng Xie;
      Pages: 1 - 5
      Abstract: The calibration of vector magnetometer arrays plays an important role in the detection of ferromagnetic targets. Traditional calibration methods assume that the magnetic environment is uniform and stable, which often is not the case. We describe a calibration method for nonuniform environments based on the redundancy of magnetic flux density tensor elements Bxy and Byx and the fact that the tensor rotational invariant remains constant at one point, independent of posture. The compensation model focuses on the gradient field, which largely eliminates geomagnetic fluctuations over time. The calibration procedure is completed at one point, which avoids problems with spatial nonuniformity of the magnetic field. Simulations confirm that the proposed calibration method provides an effective and more accurate compensation performance in inhomogeneous magnetic environments.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Integrated Magnetic Sensor Probe and Excitation Wire for Nondestructive
           Detection of Submillimeter Defects
    • Authors: Keiji Tsukada;Hiroto Shobu;Yuto Goda;Takumi Kobara;Kenji Sakai;Toshihiko Kiwa;Mohd Mawardi Saari;
      Pages: 1 - 5
      Abstract: Eddy current testing with excitation and pickup coils is widely used to detect defects in metals. The detection of submillimeter defects is difficult because of limitations on pickup coil size. We have developed an integrated magnetic probe for detecting submillimeter defects in both nonmagnetic and ferromagnetic materials. The sensor probe consists of a tunneling magnetoresistance (TMR) device and an excitation wire. This probe can apply small, localized magnetic fields to a sample that is near the TMR sensor. The direction of the field excitation is perpendicular to the sensing direction of the TMR sensor to minimize magnetic coupling between the excitation wire and the sensor. A change in the line-scanned signal was detected when measuring pits from 0.5 mm to 1.0 mm in diameter at depths of more than 0.1 mm in both steel and aluminum plates. Signal changes depended on defect size. As the frequency was increased from 1 kHz to 50 kHz, the defect signal change for the aluminum plate increased due to an increase in eddy currents. A clear defect signal for the steel plate was obtained even at a low frequency of 1 kHz because the detected signal for steel consists of a frequency-dependent eddy-current component and a magnetization component even at low frequencies.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Machine-Learning Detection Algorithms for Large Barkhausen Jumps in
           Cluttered Environment
    • Authors: Roger Alimi;Amir Ivry;Elad Fisher;Eyal Weiss;
      Pages: 1 - 5
      Abstract: Modern magnetic sensor arrays conventionally use state-of-the-art low-power magnetometers such as parallel and orthogonal fluxgates. Low-power fluxgates tend to have large Barkhausen jumps that appear as a dc jump in the fluxgate output. This phenomenon deteriorates the signal fidelity and effectively increases the internal sensor noise. Even if sensors that are more prone to dc jumps can be screened out during production, the conventional noise measurement does not always catch the dc jumps because of their sparsity. Moreover, dc jumps persist in almost all the sensor cores although at a slower but still intolerable rate. Even if dc jumps could be easily detected in a shielded environment, when deployed in the presence of natural noise and clutter, it can be hard to positively detect them. This letter fills this gap and presents algorithms that distinguish dc jumps embedded in natural magnetic field data. To improve resistance to noise, we developed two machine-learning algorithms that employ temporal and statistical physical-based features of a preacquired and well-known experimental dataset. The first algorithm employs a support vector machine classifier, while the second is based on a neural network architecture. We compare these new approaches to a more classical kernel-based method. To that purpose, the receiver operating characteristic curve is generated, which allows diagnosis ability of the different classifiers by comparing their performances across various operation points. The accuracy of the machine-learning-based algorithms over the classic method and the rapid convergence of the corresponding receiver operating characteristic curves are demonstrated.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Photoinduced Hall Effect for Low-Temperature Magnetic Sensing
    • Authors: Teslim Ayinde Fasasi;Valerio Apicella;Dong Li;Antonio Ruotolo;
      Pages: 1 - 4
      Abstract: Some low-temperature magnetic sensors are based on the Hall effect in thin metallic films. However, their sensitivity is more than one order of magnitude smaller than that of silicon-based Hall sensors operating at room temperature. Furthermore, in order to avoid significant Joule heating, only very small bias currents can be injected at low temperatures. Here, we show that a sensor based on a photoinduced Hall effect, in which charge is photogenerated in a semiconductor and injected into an adjacent metallic layer, can be used as a bias-free, cryogenic sensor. The system consists of a platinum thin film deposited on intrinsic-silicon substrate. The film forms a Schottky interface with the semiconductor. At room temperature, carriers photogenerated in the semiconductor are injected into the metal, because of rounding-off of the Schottky barrier, and are deflected by a magnetic field applied in the film plane. At cryogenic temperatures, and well below the freeze-out temperature for silicon, the photogenerated electrons can tunnel through the barrier, and the sensor recovers the same sensitivity as that obtained at room temperature.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Compact Manganite-Graphene Magnetoresistive Sensor
    • Authors: Nerija Zurauskiene;Rasuole Lukose;Saulius Balevicius;Voitech Stankevic;Skirmantas Kersulis;Valentina Plausinaitiene;Milita Vagner;Romualdas Navickas;
      Pages: 1 - 5
      Abstract: A magnetic field sensor based on a manganite/Al2O3-substrate/three-layer graphene structure operating in the range of 0.1-20 T was designed and fabricated. The La0.9Sr0.1Mn1.2O3 (LSMO) manganite film and graphene layers were prepared on the opposite sides of polycrystalline Al2O3 substrate, which enabled scaling of the effective volume of the device to about 0.16 mm3. The combination of two materials-graphene with positive magnetoresistance (MR) and manganite with negative MR-led to a significant increase of the response signal and sensitivity compared with individual graphene or manganite sensors. This was achieved by increasing the MR of the individual manganite and graphene elements. The MR of LSMO was increased by using pulsed-injection metal-organic chemical vapor deposition based on two precursor sources with tunable vapor supersaturation and growth rate. The MR of three-layer graphene was optimized by changing the width/length ratio of the rectangular planar configuration and scaling the dimensions from millimeters to few hundred micrometers. The result was a maximal sensitivity of 72 mV/VT in the field range of 1-3 T.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Intrinsic Coercivity of Very Hard Nd–Fe–B Magnets Enlarged by
           Electromagnet Measurements
    • Authors: Duxing Chen;Yonghong Zhu;
      Pages: 1 - 4
      Abstract: The intrinsic coercivity of Nd-Fe-B permanent magnets measured by the electromagnet method is substantially enlarged if it is close to or greater than the saturation magnetization of the electromagnet pole caps. This enlargement is caused by a dominant demagnetizing field against overall magnetic reversal.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Planar Hall Resistance Sensor With Improved Thermal Stability
    • Authors: Taehyeong Jeon;Jae Hoon Lee;Artem Talantsev;Cheol Gi Kim;
      Pages: 1 - 5
      Abstract: High thermal stability of the planar Hall resistance (PHR) signal in magnetic sensors, configured as a cross-junction and as a Wheatstone bridge, has been demonstrated. The thermal drift of the PHR signal, which is proportional to the PHR offset at zero field, is few orders of magnitude less than the thermal drift of the anisotropic magnetoresistance signal. The thermal drift of the PHR originates from two independent components: baseline drift and signal amplitude drift. The temperature coefficient of baseline drift, normalized by zero-field offset, is similar to the temperature coefficient of resistance. This makes it possible to characterize drift in any temperature range by a single measurement of PHR under ambient conditions. Signal amplitude drift is shown to be dependent on a sensor's geometry, and becomes higher with a reduction of the width of the current path. The temperature coefficients of baseline drift and signal amplitude drift are of opposite sign. The possibility of mutual compensation of signal amplitude drift and baseline drift by a slight imbalance in a bridge-type sensor is demonstrated.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Correlation Between Intensity of Magnetic Barkhausen Noise and Grain
           Boundaries in Grain-Oriented Electrical Steel
    • Authors: Vitor F. Oliveira;Julio C. Teixeira;Daniel A. Pereira;
      Pages: 1 - 4
      Abstract: High-permeability grain-oriented (HGO) electrical steel constitutes the best option for transformer cores because the magnetic flux can be aligned to the easy magnetizing axis of the material, therefore reducing the transformer energy loss. In this type of steel, magnetic Barkhausen noise (MBN) evaluation serves as a quality indicator for magnetic properties because it probes the loss process along the hysteresis loop. It is shown that MBN characterization can also be used as an indicator of grain size and distribution, but the strategy to correlate MBN with the polycrystalline structure differs from that of other studies, which sometimes present contradictory results restricted to the tested materials. By evaluating the MBN in HGO steel samples as a function of surface position, it is possible to show that the local intensity of the phenomenon forms contour lines that follow the grain distribution. This finding can be further used to indirectly estimate the grain size of a sample without the need of surface treatment. A specific MBN sensor was developed to obtain detailed measurements with reliable results.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Pressure Dependence of the High-Frequency Impedance of NiFe/Cu/NiFe/Cu/Cr
           Multilayer Films
    • Authors: Tao Wang;Bicong Wang;Xinge Fu;
      Pages: 1 - 5
      Abstract: A large pressure-impedance effect was measured in soft ferromagnetic NiFe/Cu/NiFe/Cu/Cr multilayer films carrying high-frequency alternating currents. Experimental results show that two pressure-impedance sensors consisting of multilayer films were highly sensitive to vertical mechanical pressures at high frequency (>50 MHz) and were capable of measuring small mechanical pressures of 0.1-0.9 gf. The resistance of the pressure-impedance sensors was greatly decreased at high frequency due to the presence of the pressures, and underwent a significant variation of -14% at 113 MHz. Large resistance variation is related to the permeability variation caused by the presence of internal stresses induced by use of mechanical pressures on NiFe films. Magnetic moment rotation caused by the mechanical pressures is probably the origin of the large variation of magnetic permeability at high frequency. The adopted pressure-impedance sensors hold great promise for sensitive measurements of mechanical pressures, such as for monitoring slight vibration, motion, and displacement.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Estimation of Angular Deviations in Precise Magnetometers
    • Authors: Michal Janosek;Elda F. Saunderson;Michal Dressler;Daniel J. Gouws;
      Pages: 1 - 5
      Abstract: Capabilities for calibrations of angular deviations of sensor triplets in precise magnetometers were evaluated in a 2.5 m, triaxial Helmholtz coil facility. The coil system is located in a magnetically quiet environment at SANSA Space Science in Hermanus, South Africa. The angular calibration results obtained from the “thin-shell” calibration procedure were compared with direct measurements on a nonmagnetic tilting/rotational platform. One-year expanded uncertainty of angular deviation calibrations is estimated as 6 × 10-2 degrees of arc; 3 × 10-4 degrees coil orthogonality is possible when doing a numerical recalibration and correction on a short-term basis. In addition, an approach for obtaining body-to-sensor angular calibrations is presented, allowing for speed-up of the calibrations and possibly increasing their accuracy and repeatability by avoiding alignment to the coils with a laser beam and leveling.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Impedance Change Ratio and Sensitivity of Micromachined Single-Layer Thin
           Film Magneto-Impedance Sensor
    • Authors: Hiroaki Kikuchi;Taisei Umezaki;Takuya Shima;Chihiro Sumida;Suguru Oe;
      Pages: 1 - 5
      Abstract: Thin-film techniques are important in the miniaturization of electronic devices. We studied a thin-film magnetoimpedance element made with Co-based amorphous soft magnetic material and developed a highly sensitive magnetic field sensor with high spatial resolution. Thin films are several micrometers thick, and show significant impedance changes as frequencies change from the megahertz to the gigahertz region. Multilayer systems are often used to achieve a large impedance change, but they typically require a complex thin-film structure and a length of several millimeters. Our thin-film sensors have lengths between 30 μm and 1 mm in a simple monolayer configuration and successfully overcome the demagnetizing field. The impedance change ratio was 300% for a 1 mm long element at 1 GHz and between 20-30% at 1 GHz for a miniaturized element of 30 μm. The sensors had a maximum sensitivity of 33.4%/Oe.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Measurement Characteristics of Different Integrated Three-Dimensional
           Magnetic Field Sensors
    • Authors: Philip Beran;Maximilian Klöhn;Hans-Peter Hohe;
      Pages: 1 - 5
      Abstract: Datasheets of different commercially available integrated sensors for vector measurements of magnetic fields provide typical specifications, such as measurement range, sampling rate, resolution, and noise. Other characteristics of interest, such as linearity, cross-sensitivity, remanent magnetization, and drifts over temperature, are mostly missing. This letter presents testing results of those characteristics of integrated three-dimensional (3-D) sensors working with different sensor principles and technologies in a reproducible measuring process. The sensors are exposed to temperatures from −20 °C to 80 °C and are cycled in hysteresis loops in fields up to 2.5 mT. For applying high-accuracy magnetic fields, a calibrated 3-D Helmholtz coil setup is used. Commercially available integrated 3-D magnetic field sensors are put in operation on a printed circuit board using nonmagnetic passive components. All sensors are configured for best measurement accuracy according to their datasheets. The results show that sensors based on anisotropic magnetoresistance have high accuracy and low offsets yet also a high degree of nonlinearity. Hall-based sensors show good linearity but also high cross-sensitivity. A magnetic remanence appears for Hall-based sensors with integrated magnetic concentrators as well as for sensors using anisotropic magnetoresistance. Nearly all sensors show remaining drifts over temperature regarding offset and sensitivity up to several percentages.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Zero Magnetic Field Calibration for Single-Beam Atomic Magnetometers Using
           Second Harmonics
    • Authors: Khanuengchat Saenyot;Yuya Shoji;Shunya Takahashi;Masahiro Daibo;
      Pages: 1 - 4
      Abstract: In this letter, we propose a simple and rapid method for zero field calibration of single elliptically polarized beam atomic magnetometers. This method uses a wobble adjustment that applies a small amplitude and low-frequency (70 Hz) ac magnetic field and sweeps the dc magnetic field. The second harmonic signal reaches its maximum when the dc magnetic field noise is zero. Our single-beam atomic magnetometer operates with elliptically polarized light, which has both circularly and linearly polarized light components. The wavelength of a single beam for a rubidium atom was determined to be 780.206 nm with a power of 2.72 mW.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Synthesis of Temperature-Sensitive Magnetic Microcapsules and
           Visualization of Cluster Formation
    • Authors: Keiko Ishii;Ryota Aizawa;Koji Fumoto;
      Pages: 1 - 4
      Abstract: Temperature-sensitive magnetic fluids flow spontaneously in a magnetic field when there is a temperature difference and thus may be used in cooling devices operated without external power. However, magnetic fluids are difficult to mass-produce, and the dispersion ability of the working fluid cannot be controlled. We use magnetic material encapsulated in microcapsules of large diameter to function as a new type of refrigerant. By enclosing the magnetic material in capsules, they can be used with any working fluid. We made solid particles containing kerosene-based magnetic fluid in polymer. When a magnetic field was applied, the particles aggregated and formed clusters. A scanning electron microscope and focused ion beam system were used to determine the particle shapes. Particles 5-50 μm in size could be created by varying the rotation speed of the homogenizer during the synthesis.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Estimation of Intrinsic Magnetic Properties of Single Particles by
           Particle Tracking Velocimetry
    • Authors: Abhinav Sannidhi;Paul Wilson Todd;Thomas R. Hanley;
      Pages: 1 - 5
      Abstract: Characterization of paramagnetic particles is of utmost importance in biotechnology, cell separations, and medical applications. The particle size uniformity and colloidal stability of paramagnetic particles have been the focus of most producers, but magnetization is never specified and is typically mentioned only in terms of percent iron oxide content. Bulk measurements of magnetic susceptibility and saturation magnetization, using a superconducting quantum interference device (SQUID) or a vibrating sample magnetometer (VSM), provide an average value at best and do not account for the distributed nature of these variables or for particles with zero or very low susceptibility and magnetization. By means of particle tracking velocimetry in dark-field illumination, we measured multiple characteristics of several thousand individual micrometer-sized particles per sample. The Hyperflux velocimeter is utilized to provide quantitative video analysis of cells and particles using a high-definition camera to capture the images of the particle trajectories in an isodynamic field. Image analysis software converts the image data to the parameters of interest based on velocimetry calculations. The intrinsic magnetic properties of the magnetic beads estimated by both the velocimeter and VSM are in good agreement. Estimation of the magnetophoretic mobility distributions and intrinsic magnetic properties of magnetic microparticles using dark-field particle tracking allows economical and time-efficient magnetic evaluation of a broad range of magnetic particle sizes.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
  • Correction to “Electrochemical Synthesis of Co-Rich Nanowires for
           Barcodes”
    • Authors: Sri Ramulu Torati;Xinghao Hu;Seok Soo Yoon;CheolGi Kim;
      Pages: 1 - 1
      Abstract: This erratum corrects scanning electron microscopy images and a magnetization curve that appeared in an article by the authors.
      PubDate: 2019
      Issue No: Vol. 10 (2019)
       
 
 
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