Pub Date : 2023-03-30DOI: 10.1109/LMAG.2023.3279778
Lise G. Hanson;Bianca L. Hansen;Thomas Veile;Mathias Zambach;Niels B. Christensen;Cathrine Frandsen
Correct estimation of the heating power of magnetic nanoparticles is important for magnetic hyperthermia treatment. This letter investigates the impact of sample insulation in ac calorimetry. We show that a temperature increase in the insulation can lead to systematic errors when estimating the heating power by the corrected slope method. The errors arise if the temperature of the sample environment is kept fixed at its initial temperature in the data analysis. To correct this, the local temperature difference between the sample and the sample environment should be used.
{"title":"The Impact of Sample Insulation on Estimating the Heating Power of Magnetic Nanoparticles by AC Calorimetry","authors":"Lise G. Hanson;Bianca L. Hansen;Thomas Veile;Mathias Zambach;Niels B. Christensen;Cathrine Frandsen","doi":"10.1109/LMAG.2023.3279778","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3279778","url":null,"abstract":"Correct estimation of the heating power of magnetic nanoparticles is important for magnetic hyperthermia treatment. This letter investigates the impact of sample insulation in ac calorimetry. We show that a temperature increase in the insulation can lead to systematic errors when estimating the heating power by the corrected slope method. The errors arise if the temperature of the sample environment is kept fixed at its initial temperature in the data analysis. To correct this, the local temperature difference between the sample and the sample environment should be used.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fine magnetic particles with high saturation magnetization and a large temperature-sensitive magnetization in the temperature range 300–400 K were prepared for use in temperature-sensitive magnetorheological fluids. Two methods, namely high-energy ball milling (HEBM) and sintering followed by HEBM to produce mechanochemical alloys, were used to produce R 2 Fe 17 component particles. The prepared particles were submicrometer- to micrometer-sized and contained rare-earth–iron alloys and α-Fe phases. Among the prepared particles, Sm 2 Fe 17 composition powder exhibited the highest temperature sensitivity of −0.02 A m 2 kg −1 K −1 at 400 K. Furthermore, powders with varying Fe and Sm composition ratios were prepared by sintering and ball milling. The powder prepared from the initial SmFe 5 composition exhibited the highest temperature sensitivity of −0.32 A m 2 kg −1 K −1 at 400 K and saturation magnetization was ∼90 A m 2 kg −1 . The powder was composed of SmFe 5 and Sm 2 Fe 17 in crystalline, α-Fe phase, and amorphous phase, as revealed by X-ray diffraction analysis and a scanning electron microscope, as well as high-resolution transmission electron microscopy with selected area electron diffraction.
制备了在300–400 K温度范围内具有高饱和磁化强度和大温敏磁化强度的精细磁性颗粒，用于温敏磁流变流体。使用两种方法，即高能球磨（HEBM）和烧结，然后用HEBM生产机械化学合金，来生产R2Fe17组分颗粒。制备的颗粒尺寸为亚微米至微米，含有稀土-铁合金和α-Fe相。在制备的颗粒中，Sm2Fe17组成的粉末在400 K下表现出最高的温度敏感性，为−0.02 A m2 kg−1 K−1。此外，通过烧结和球磨制备了不同Fe和Sm组成比的粉末。由初始SmFe5成分制备的粉末在400 K下表现出最高的温度敏感性，为−0.32 A m2 kg−1 K−1，饱和磁化强度为~90 A m2 kg-1。X射线衍射分析和扫描电子显微镜以及选区电子衍射的高分辨率透射电子显微镜显示，该粉末由结晶相、α-Fe相和非晶相的SmFe5和Sm2Fe17组成。
{"title":"Preparation of Temperature-Sensitive Rare-Earth–Iron Alloy Fine Particles Using Mechanical Alloying and Sintering","authors":"Jiatong Pan;Jianfei Shentu;Chunlin He;Deqian Zeng;Feng Gao;Gjergj Dodbiba;Toyohisa Fujita","doi":"10.1109/LMAG.2023.3281158","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3281158","url":null,"abstract":"Fine magnetic particles with high saturation magnetization and a large temperature-sensitive magnetization in the temperature range 300–400 K were prepared for use in temperature-sensitive magnetorheological fluids. Two methods, namely high-energy ball milling (HEBM) and sintering followed by HEBM to produce mechanochemical alloys, were used to produce R\u0000<sub>2</sub>\u0000Fe\u0000<sub>17</sub>\u0000 component particles. The prepared particles were submicrometer- to micrometer-sized and contained rare-earth–iron alloys and α-Fe phases. Among the prepared particles, Sm\u0000<sub>2</sub>\u0000Fe\u0000<sub>17</sub>\u0000 composition powder exhibited the highest temperature sensitivity of −0.02 A m\u0000<sup>2</sup>\u0000 kg\u0000<sup>−1</sup>\u0000 K\u0000<sup>−1</sup>\u0000 at 400 K. Furthermore, powders with varying Fe and Sm composition ratios were prepared by sintering and ball milling. The powder prepared from the initial SmFe\u0000<sub>5</sub>\u0000 composition exhibited the highest temperature sensitivity of −0.32 A m\u0000<sup>2</sup>\u0000 kg\u0000<sup>−1</sup>\u0000 K\u0000<sup>−1</sup>\u0000 at 400 K and saturation magnetization was ∼90 A m\u0000<sup>2</sup>\u0000 kg\u0000<sup>−1</sup>\u0000. The powder was composed of SmFe\u0000<sub>5</sub>\u0000 and Sm\u0000<sub>2</sub>\u0000Fe\u0000<sub>17</sub>\u0000 in crystalline, α-Fe phase, and amorphous phase, as revealed by X-ray diffraction analysis and a scanning electron microscope, as well as high-resolution transmission electron microscopy with selected area electron diffraction.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Crystal Structure and Magnetic Properties of Hexagonal FeCo Nitrides Prepared Using Ammonia Gas Nitrification","authors":"Chihiro Kodaka;Mikio Kishimoto;Eiji Kita;Hideto Yanagihara","doi":"10.1109/LMAG.2023.3262452","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3262452","url":null,"abstract":"Single-phase <inline-formula><tex-math notation=\"LaTeX\">$varepsilon$</tex-math></inline-formula>-(FeCo)<italic><sub>x</sub></italic>N compound particles with <inline-formula><tex-math notation=\"LaTeX\">$x$</tex-math></inline-formula> = 2.25–2.48 were synthesized using ammonia gas nitrification. The mass magnetization <inline-formula><tex-math notation=\"LaTeX\">$M$</tex-math></inline-formula> at 10 K under a magnetic field of 9 T was 77 A<inline-formula><tex-math notation=\"LaTeX\">$cdot$</tex-math></inline-formula>m<inline-formula><tex-math notation=\"LaTeX\">$^{2}$</tex-math></inline-formula>/kg, and Curie temperature <inline-formula><tex-math notation=\"LaTeX\">$T$</tex-math></inline-formula><sub>C</sub> was 100 K for <inline-formula><tex-math notation=\"LaTeX\">$x$</tex-math></inline-formula> = 2.48. These values decreased with increasing nitrogen content. Compared with <inline-formula><tex-math notation=\"LaTeX\">$varepsilon$</tex-math></inline-formula>-Fe<italic><sub>x</sub></italic>N, (FeCo)<italic><sub>x</sub></italic>N had significantly lower <inline-formula><tex-math notation=\"LaTeX\">$M$</tex-math></inline-formula> and <inline-formula><tex-math notation=\"LaTeX\">$T$</tex-math></inline-formula><sub>C</sub> values, even at comparable nitrogen content. Mössbauer spectroscopy suggests that the magnetic moment of Co decreases with increasing nitrogen content and disappears at approximately <inline-formula><tex-math notation=\"LaTeX\">$x$</tex-math></inline-formula> = 2.35, even at the lowest measurement temperature of <inline-formula><tex-math notation=\"LaTeX\">$T$</tex-math></inline-formula> = 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 <inline-formula><tex-math notation=\"LaTeX\">$x$</tex-math></inline-formula> = 2.25 when the nitrogen content is low.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67762120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-25DOI: 10.1109/LMAG.2023.3280120
Zulfidin Khodzhaev;Emrah Turgut;Jean Anne C. Incorvia
In this study, micromagnetic simulations of a magnetic skyrmion reshuffling chamber for probabilistic computing applications are performed. The skyrmion shuffling chamber is modeled with a custom current density masking technique to capture current density variation, grain boundary variations, and anisotropy changes. The results show that the skyrmion oscillatory dynamics contribute to the system's stochasticity, allowing uncorrelated signals to be achieved with a single chamber. Our findings indicate that uncorrelated signals are generally achieved at all temperatures simulated, with the skyrmion diameter playing a role in the resulting stochasticity. Furthermore, we find that local temperature control has the benefit of not affecting the overall skyrmion diameter, while still perturbing the skyrmion trajectory. The results from varying chamber size, global temperature, and local temperature are analyzed using Pearson correlation coefficient and p-value. This research contributes to the development of tunable probabilistic computing devices and artificial synapses using magnetic skyrmions.
{"title":"Analysis of Skyrmion Shuffling Chamber Stochasticity for Neuromorphic Computing Applications","authors":"Zulfidin Khodzhaev;Emrah Turgut;Jean Anne C. Incorvia","doi":"10.1109/LMAG.2023.3280120","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3280120","url":null,"abstract":"In this study, micromagnetic simulations of a magnetic skyrmion reshuffling chamber for probabilistic computing applications are performed. The skyrmion shuffling chamber is modeled with a custom current density masking technique to capture current density variation, grain boundary variations, and anisotropy changes. The results show that the skyrmion oscillatory dynamics contribute to the system's stochasticity, allowing uncorrelated signals to be achieved with a single chamber. Our findings indicate that uncorrelated signals are generally achieved at all temperatures simulated, with the skyrmion diameter playing a role in the resulting stochasticity. Furthermore, we find that local temperature control has the benefit of not affecting the overall skyrmion diameter, while still perturbing the skyrmion trajectory. The results from varying chamber size, global temperature, and local temperature are analyzed using Pearson correlation coefficient and p-value. This research contributes to the development of tunable probabilistic computing devices and artificial synapses using magnetic skyrmions.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67762072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-08DOI: 10.1109/LMAG.2023.3274051
Md Golam Morshed;Samiran Ganguly;Avik W. Ghosh
Low energy barrier magnet (LBM) technology has recently been proposed as a candidate for accelerating algorithms based on energy minimization and probabilistic graphs because their physical characteristics have a one-to-one mapping onto the primitives of these algorithms. Many of these algorithms have a much higher tolerance for error compared to high-accuracy numerical computation. LBM, however, is a nascent technology, and devices show high sample-to-sample variability. In this letter, we take a deep dive into the overall fidelity afforded by this technology in providing computational primitives for these algorithms. We show, that while the computed results show finite deviations from zero-variability devices, the margin of error is almost always certifiable to a certain percentage. This suggests that LBM technology could be a viable candidate as an accelerator for popular emerging paradigms of computing.
{"title":"A Deep Dive Into the Computational Fidelity of High-Variability Low Energy Barrier Magnet Technology for Accelerating Optimization and Bayesian Problems","authors":"Md Golam Morshed;Samiran Ganguly;Avik W. Ghosh","doi":"10.1109/LMAG.2023.3274051","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3274051","url":null,"abstract":"Low energy barrier magnet (LBM) technology has recently been proposed as a candidate for accelerating algorithms based on energy minimization and probabilistic graphs because their physical characteristics have a one-to-one mapping onto the primitives of these algorithms. Many of these algorithms have a much higher tolerance for error compared to high-accuracy numerical computation. LBM, however, is a nascent technology, and devices show high sample-to-sample variability. In this letter, we take a deep dive into the overall fidelity afforded by this technology in providing computational primitives for these algorithms. We show, that while the computed results show finite deviations from zero-variability devices, the margin of error is almost always certifiable to a certain percentage. This suggests that LBM technology could be a viable candidate as an accelerator for popular emerging paradigms of computing.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-08DOI: 10.1109/LMAG.2023.3274049
Thao Huong Pham
Possible average alignments of the spins in the ground state and the phase transitions of a geometrically frustrated Ising antiferromagnet in the presence of magnetic fields on a triangular lattice are studied in a mean field approximation. Starting from a zero-field clock phase, we can determine the phase boundaries from the curves of magnetic moments and their derivatives as functions of the fields. We also analyze the behavior of sublattice magnetic moments under the effect of the fields. The experimental relevances for TmMgGaO 4 and SrEr 2 O 4 are discussed. Besides, using a functional integral method, we have calculated a functional for free energy to obtain the contribution of spin fluctuations. From this, we can find that the role of the quantum spin fluctuations at very low temperatures is only prominent in the vicinity of the transition points. It can therefore be seen that the results, although given in the mean field approximation, describe quite well the phase transitions and rearrangements of the magnetic moment per spin under the effect of both the transverse and longitudinal fields.
{"title":"Possible Ground States and Magnetic-Field-Tuned Phase Transitions of a Geometrically Frustrated Ising Antiferromagnet on a Triangular Lattice","authors":"Thao Huong Pham","doi":"10.1109/LMAG.2023.3274049","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3274049","url":null,"abstract":"Possible average alignments of the spins in the ground state and the phase transitions of a geometrically frustrated Ising antiferromagnet in the presence of magnetic fields on a triangular lattice are studied in a mean field approximation. Starting from a zero-field clock phase, we can determine the phase boundaries from the curves of magnetic moments and their derivatives as functions of the fields. We also analyze the behavior of sublattice magnetic moments under the effect of the fields. The experimental relevances for TmMgGaO\u0000<sub>4</sub>\u0000 and SrEr\u0000<sub>2</sub>\u0000O\u0000<sub>4</sub>\u0000 are discussed. Besides, using a functional integral method, we have calculated a functional for free energy to obtain the contribution of spin fluctuations. From this, we can find that the role of the quantum spin fluctuations at very low temperatures is only prominent in the vicinity of the transition points. It can therefore be seen that the results, although given in the mean field approximation, describe quite well the phase transitions and rearrangements of the magnetic moment per spin under the effect of both the transverse and longitudinal fields.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67762118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-09DOI: 10.1109/LMAG.2023.3243493
Kota Nomura;Masaomi Washino;Tetsuya Matsuda;Shun Tonooka;Seino Satoshi;H. Yoshida;K. Nishigaki;Takashi Nakagawa;Toshihiko Kiwa
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.
{"title":"Magnetic-Particle-Discrimination Method Using Difference of Relaxation Time for Magnetic Particle Imaging","authors":"Kota Nomura;Masaomi Washino;Tetsuya Matsuda;Shun Tonooka;Seino Satoshi;H. Yoshida;K. Nishigaki;Takashi Nakagawa;Toshihiko Kiwa","doi":"10.1109/LMAG.2023.3243493","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3243493","url":null,"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.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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 Fe 85 Si 2 B 8 P 4 Cu 1 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 angular dependence of magnetic scattering would be helpful to considering the relationship between partially nanocrystallized structure and macroscopic soft magnetic properties.
{"title":"Magnetic Structural Analysis of Nanocrystalline Soft Magnets by Small-Angle Neutron Scattering","authors":"Hiroaki Mamiya;Yojiro Oba;Kosuke Hiroi;Takayuki Miyatake;Ravi Gautam;Hossein Sepehri-Amin;Tadakatsu Ohkubo","doi":"10.1109/LMAG.2023.3242108","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3242108","url":null,"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 Fe\u0000<sub>85</sub>\u0000Si\u0000<sub>2</sub>\u0000B\u0000<sub>8</sub>\u0000P\u0000<sub>4</sub>\u0000Cu\u0000<sub>1</sub>\u0000 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 \u0000<italic>q</i>\u0000 in proportion to \u0000<italic>q</i>\u0000<sup>−4</sup>\u0000, 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 \u0000<italic>q</i>\u0000 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 angular dependence of magnetic scattering would be helpful to considering the relationship between partially nanocrystallized structure and macroscopic soft magnetic properties.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Hybrid MTJ/CNTFET-Based Binary Synapse and Neuron for Process-in-Memory Architecture","authors":"Milad Tanavardi Nasab;Arefe Amirany;Mohammad Hossein Moaiyeri;Kian Jafari","doi":"10.1109/LMAG.2023.3238271","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3238271","url":null,"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.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-16DOI: 10.1109/LMAG.2023.3237384
Angelika S. Thalmayer;Kilian Götz;Samuel Zeising;Georg Fischer
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.
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