 Subjects -> ELECTRONICS (Total: 207 journals)
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- Crystal Structure and Magnetic Properties of Hexagonal FeCo Nitrides
Prepared Using Ammonia Gas Nitrification-
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Authors:
Chihiro Kodaka;Mikio Kishimoto;Eiji Kita;Hideto Yanagihara;
Pages: 1 - 5
Abstract: Single-phase $varepsilon$-(FeCo)xN compound particles with $x$ = 2.25–2.48 were synthesized using ammonia gas nitrification. The mass magnetization $M$ at 10 K under a magnetic field of 9 T was 77 A$cdot$m$^{2}$/kg, and Curie temperature $T$C was 100 K for $x$ = 2.48. These values decreased with increasing nitrogen content. Compared with $varepsilon$-FexN, (FeCo)xN had significantly lower $M$ and $T$C values, even at comparable nitrogen content. Mössbauer spectroscopy suggests that the magnetic moment of Co decreases with increasing nitrogen content and disappears at approximately $x$ = 2.35, even at the lowest measurement temperature of $T$ = 3 K. Griffiths phaselike magnetic behavior was observed in the temperature dependence of magnetic susceptibility. The experimental results indicate that the Fe–Fe interaction may change from ferromagnetic to antiferromagnetic at $x$ = 2.25 when the nitrogen content is low.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Numerical Study on the Magnetization Characteristics of Chainlike Magnetic
Nanoparticles-
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Authors:
Haochen Zhang;Yi Sun;Zhongzhou Du;Teruyoshi Sasayama;Takashi Yoshida;
Pages: 1 - 4
Abstract: This work investigated chainlike magnetic nanoparticles (CMNPs), which are a type of magnetic nanoparticle (MNP) with a dipole–dipole interaction in which individual nanoparticles are connected to form a chainlike structure. We numerically analyzed the ac magnetization characteristics of the CMNP and the single-core MNP (SMNP) using the Landau–Lifshitz–Gilbert equation. Owing to the magnetic dipole–dipole interaction, the magnetization of the CMNP is approximately 10 times that of the SMNP under a certain excitation field. MNPs with a chainlike structure are thus expected to have enhanced magnetization characteristics and better performance in medical applications. Additionally, it was found that stronger magnetization can be expected from a CMNP connecting 10 or more magnetic cores with a size of approximately 10–12 nm.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Impact of Array Length on Particle Attraction in Magnetic Drug Targeting:
Investigation Using an Exponential Approximation of the Magnetic Field-
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Authors:
Angelika S. Thalmayer;Kilian Götz;Samuel Zeising;Georg Fischer;
Pages: 1 - 5
Abstract: In magnetic drug targeting, special magnetic nanoparticles that carry the anticancer drug are injected into the cardiovascular system in the vicinity of the tumor and are navigated into the tumor using a magnetic field. Many researchers optimize single magnets for this purpose; however, magnetic arrays that are placed parallel to the vessel in order to increase the impact time of the magnetic force on the particles are also discussed. To the best of the authors' knowledge, the improvement by the increased impact time has not been studied in detail so far and, thus, will be addressed in this work. In this context, an artificial exponential magnetic field that approximates the field of a Halbach array and acts as an upper limit consideration is applied to different impact lengths within a predefined magnetic domain. To compare the impact of the field parameters, the total magnetic energetic effort is kept constant as a reference for studying variations of impact length. The results reveal that a longer impact length increases the attraction performance enormously. However, for the same magnetic effort, a longer impact length with a lower magnetic field strength leads to the same attraction of the particles as a shorter one with higher field strengths. Since it is easier to generate lower field strengths, the usage of arrays to realize a longer impact length is preferable.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Magnetic Field Enhancement of Water Evaporation in Confined Spaces
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Authors:
Sruthy Poulose;Yara Alvarez-Braña;Lourdes Basabel-Desmonts;Fernando Benito-Lopez;John Michael David Coey;
Pages: 1 - 5
Abstract: Water is studied in confined environments where it evaporates into its own vapor. Simultaneous experiments are conducted for 0.4–0.5 µL droplets confined at the center of 54 mm long microchannels with a cross section of 0.38 mm2 in the presence and absence of a 300 mT magnetic field. Results are compared with those for water in half-filled 100 mL beakers. The magnetic enhancement of the evaporation rate is much greater in the microchannels, where effects range up to 140% even though the air is saturated with water vapor, as compared to 12 ± 7% in a 500 mT field in the beakers. The average steady state, no-field evaporation rate of 0.13 kg$cdot$m−2$cdot$h−1 in the microchannels is roughly double that in the beakers, but less than the value expected at an open surface in still air. The magnetic enhancement is analyzed in terms of the ortho and para nuclear isomers of water vapor, which behave as independent gasses. The ortho:para ratio in fresh vapor is close to 2:3, and quite different from the 3:1 equilibrium ratio in ambient air. Evaporation is increased by the gradient of the applied magnetic field, which dephases the Larmor precession of the two proton spins of hydrogen in a water molecule and tends to equalize the isomeric populations in the vapor, thereby increasing the evaporation rate.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Hybrid MTJ/CNTFET-Based Binary Synapse and Neuron for
Process-in-Memory Architecture-
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Authors:
Milad Tanavardi Nasab;Arefe Amirany;Mohammad Hossein Moaiyeri;Kian Jafari;
Pages: 1 - 5
Abstract: This letter develops a reliable, integrated binary synapse and neuron model for hardware implementation of binary neural networks. Thanks to the nonvolatile nature of magnetic tunnel junctions and the unique features of carbon nanotube field-effect transistors, the modeled design does not require external memory to store weights and also consumes low static power. Also, due to the circuit structure, which did not use sequential parts, the developed circuit is immune to soft error. Because, in binary neural networks, weights are limited to two values of −1 and 1, the occurrence of soft errors dramatically reduces the accuracy of the network. Simulation results indicate that the design in this work consumes at least 9% lower power, occupies 34% lower area, and offers a 49% lower power delay area product. Also, Monte Carlo simulations have been performed to study the effect of the process variation on the network. The result of the Monte Carlo simulations shows that the proposed neuron has no logical error in 10 000 simulations. Consequently, the accuracy of the network utilization by the neuron is equal to the software-implemented network and does not decrease even in the presence of process variations.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Investigation of Impact of the Annealing on Magnetothermal Properties of
Zn0.2Mn0.8Fe2O4 Nanoparticles-
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Authors:
Nan N. Liu;Yulia A. Alekhina;Alexander P. Pyatakov;Nikolai S. Perov;Boris B. Kovalev;Gleb B. Sukhorukov;Alexander M. Tishin;Tomomasa Moriwaki;Kenta Nakazawa;Yuko Ichiyanagi;
Pages: 1 - 5
Abstract: Magnetic and magnetothermal properties of annealed Zn0.2Mn0.8Fe2O4 nanoparticles with diameter value, ranging from 9 to 35 nm, have been investigated and compared with earlier investigated unannealed Zn0.2Mn0.8Fe2O4 magnetic nanoparticles (MNPs). A single-phase spinel structure was observed in both types of MNPs. It has been demonstrated that for the large annealed Zn0.2Mn0.8Fe2O4 nanoparticles (24.7, 31.4, 35.1 nm) the value of specific absorption rate (SAR) is proportional to the amplitude of the magnetic field as ∼H4. However, for earlier investigated unannealed Zn0.2Mn0.8Fe2O4 MNPs, superquadratic dependence SAR ∼H5 have been found starting from 13 nm. Significant change of dependence of the character of SAR(d) may be explained by low values of hysteresis area of small annealed MNPs and, thus, dominant role of Néel relaxation in these annealed Zn0.2Mn0.8Fe2O4 nanoparticles.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Magnetic Structural Analysis of Nanocrystalline Soft Magnets by
Small-Angle Neutron Scattering-
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Authors:
Hiroaki Mamiya;Yojiro Oba;Kosuke Hiroi;Takayuki Miyatake;Ravi Gautam;Hossein Sepehri-Amin;Tadakatsu Ohkubo;
Pages: 1 - 5
Abstract: Nanocrystalline soft magnets have attracted significant attention for their improvement of energy conversion devices. It has been considered that the partial nanocrystallization of amorphous structures is a key to macroscopic magnetic softness. However, the mechanism has not been clarified because of inadequate knowledge of the magnetic nanostructures connecting microscopic crystalline structures and macroscopic magnetic properties. Here, we performed small-angle neutron scattering (SANS) for Fe85Si2B8P4Cu1 alloy ribbons (NANOMETs). Rapidly quenched ribbons were annealed at 375 °C and 400 °C for 5 min. The X-ray diffraction pattern for the as-quenched ribbons did not exhibit peaks. Therefore, their atomic structure can be considered amorphous. Oppositely, evident α-iron peaks were observed for the ribbons annealed at 375 °C and 400 °C. The nuclear scattering contribution in SANS indicates that the precipitations were formed with sizes in the nanoscale. The magnetic scattering contribution in SANS for the as-quenched ribbon, whose intensity decreased with an increase in the scattering vector q in proportion to q−4, disappeared when magnetic fields were applied. This behavior is consistent with the conventional magnetic domain picture. Oppositely, the reduction rates of the magnetic scattering contribution for q were nonmonotonous for the nanocrystallized ribbons. Furthermore, strong magnetic scattering was observed in the directions inclined to the magnetic field. This feature is similar to that reported for Fe–(Nb, Zr)–B alloy ribbons (NANOPERMs). The knowledge on the magnetic nanostructures characterized by the unusual angula- dependence of magnetic scattering would be helpful to considering the relationship between partially nanocrystallized structure and macroscopic soft magnetic properties.
PubDate:
2023
Issue No: Vol. 14 (2023)
- Magnetic-Particle-Discrimination Method Using Difference of Relaxation
Time for Magnetic Particle Imaging-
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Authors:
Kota Nomura;Masaomi Washino;Tetsuya Matsuda;Shun Tonooka;Seino Satoshi;H. Yoshida;K. Nishigaki;Takashi Nakagawa;Toshihiko Kiwa;
Pages: 1 - 5
Abstract: Magnetic particle imaging (MPI) is an imaging modality that directly detects the nonlinear responses of magnetic nanoparticles (MNPs). Spatial encoding is achieved by saturating the magnetic moment of MNPs almost everywhere except in a special point called the field-free region in which a magnetic field vanishes. Recently, MPI sensitivity was improved using a field-free line (FFL) in which a field-free region was formed as a line. An MPI with an FFL device was developed using a neodymium magnet and an iron yoke to image objects with a small amount of MNPs, such as in biological systems. We have been developing MPI equipment for detecting amyloid-β, a causative agent of Alzheimer's disease. We attached amyloid-β probes to nanoparticles. In our development, we discriminated between magnetic particles that are bound to biological tissue from those that are suspended in the brain. We focused on the differences in relaxation times due to the change in the hydrodynamic diameter between the bound and unbound particles. Because the bound particles have a larger apparent particle size and do not rotate when an ac magnetic field is applied, the relaxation time is different from the unbound particles. Since the differences in the responses to the ac magnetic field appear as relaxation times, we investigated a particle-discrimination method using these differences and studied the magnetization response of MNPs using our developed MPI device.
PubDate:
2023
Issue No: Vol. 14 (2023)
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