The purpose of this study is to develop a magnetic particle imaging (MPI) technique to directly measure time-varied cerebral superparamagnetic iron oxide nanoparticle (SPIO) concentration in rhesus macaques. A hand-held MPI detector was developed to monitor MPI signal changes at the third harmonics of the drive frequency in resting-state nonhuman primates. Phantom experiments were first performed to determine the sensitivity limits of the detector as a function of distance from the detector and SPIO concentration. The measured sensitivity profile was then used to reveal the most sensitive region of the detector. MPI detection was continuously performed to monitor MPI signal changes after two bolus injections of SPIOs in the rhesus macaque. We successfully developed a hand-held MPI to detect cerebral SPIO concentration changes in a living nonhuman primate. The detection limit of the MPI detector is about 125 ng iron. We reported on the in vivo measurement of cerebral SPIO concentration changes in rhesus macaque using a hand-held MPI detector. In vivo experiments showed the feasibility of the detector to sensitively measure MPI signals in a nonhuman primate brain.
{"title":"In Vivo Measurement of Cerebral SPIO Concentration in Nonhuman Primate Using Magnetic Particle Imaging Detector","authors":"Hui Hui;Jiaojiao Liu;Hui Zhang;Jing Zhong;Jie He;Bo Zhang;Haoran Zhang;Qin Li;Hongjun Li;Jie Tian","doi":"10.1109/LMAG.2023.3281933","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3281933","url":null,"abstract":"The purpose of this study is to develop a magnetic particle imaging (MPI) technique to directly measure time-varied cerebral superparamagnetic iron oxide nanoparticle (SPIO) concentration in rhesus macaques. A hand-held MPI detector was developed to monitor MPI signal changes at the third harmonics of the drive frequency in resting-state nonhuman primates. Phantom experiments were first performed to determine the sensitivity limits of the detector as a function of distance from the detector and SPIO concentration. The measured sensitivity profile was then used to reveal the most sensitive region of the detector. MPI detection was continuously performed to monitor MPI signal changes after two bolus injections of SPIOs in the rhesus macaque. We successfully developed a hand-held MPI to detect cerebral SPIO concentration changes in a living nonhuman primate. The detection limit of the MPI detector is about 125 ng iron. We reported on the \u0000<italic>in vivo</i>\u0000 measurement of cerebral SPIO concentration changes in rhesus macaque using a hand-held MPI detector. \u0000<italic>In vivo</i>\u0000 experiments showed the feasibility of the detector to sensitively measure MPI signals in a nonhuman primate brain.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/iel7/5165412/10018138/10141661.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67762116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-20DOI: 10.1109/LMAG.2023.3268851
Atsuki Kobayashi;Kohya Sano;Junpei Sakurai;Hosei Nagano;Seiichi Hata;Chiemi Oka
We present a novel manufacturing technique for generating unidirectional pores in ultraviolet (UV)-curable resins using self-assembled magnetic nanoparticles (MNPs) with chain-like structures. The method utilizes two templation mechanisms for pore formation: the UV-masking effect of the MNP chains and the physical presence of MNP chains themselves. Fe 3 O 4 nanoparticles and PAK-01 were used as the template and UV-curable resin, respectively. Unidirectional pores formed only when resin/MNP mixtures were cured under a strong externally applied magnetic field. Water absorption tests indicated that some of the unidirectional pores were through-hole-type pores. The pores were cylindrical with an ellipsoidal cross-section. When the UV irradiation angle ( θ ) was 30°, the long and short diameters of the pores were approximately 9 and 8 $mu$ m, respectively, before MNP removal, and 12 and 8 $mu$ m, respectively, after removal. After MNP removal, the ellipticity of the pores in the samples increased from 1.5 to 2.4 with the increase in θ because of the increased UV-masking effect of the MNP chains.
{"title":"Unidirectional Pore Formation in Resins Using a Magnetic-Nanoparticle-Chain Template","authors":"Atsuki Kobayashi;Kohya Sano;Junpei Sakurai;Hosei Nagano;Seiichi Hata;Chiemi Oka","doi":"10.1109/LMAG.2023.3268851","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3268851","url":null,"abstract":"We present a novel manufacturing technique for generating unidirectional pores in ultraviolet (UV)-curable resins using self-assembled magnetic nanoparticles (MNPs) with chain-like structures. The method utilizes two templation mechanisms for pore formation: the UV-masking effect of the MNP chains and the physical presence of MNP chains themselves. Fe\u0000<sub>3</sub>\u0000O\u0000<sub>4</sub>\u0000 nanoparticles and PAK-01 were used as the template and UV-curable resin, respectively. Unidirectional pores formed only when resin/MNP mixtures were cured under a strong externally applied magnetic field. Water absorption tests indicated that some of the unidirectional pores were through-hole-type pores. The pores were cylindrical with an ellipsoidal cross-section. When the UV irradiation angle (\u0000<italic>θ</i>\u0000) was 30°, the long and short diameters of the pores were approximately 9 and 8 \u0000<inline-formula><tex-math>$mu$</tex-math></inline-formula>\u0000m, respectively, before MNP removal, and 12 and 8 \u0000<inline-formula><tex-math>$mu$</tex-math></inline-formula>\u0000m, respectively, after removal. After MNP removal, the ellipticity of the pores in the samples increased from 1.5 to 2.4 with the increase in \u0000<italic>θ</i>\u0000 because of the increased UV-masking effect of the MNP chains.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763011","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 : 2023-04-04DOI: 10.1109/LMAG.2023.3262976
Sruthy Poulose;Yara Alvarez-Braña;Lourdes Basabel-Desmonts;Fernando Benito-Lopez;John Michael David Coey
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 mm 2 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.
{"title":"Magnetic Field Enhancement of Water Evaporation in Confined Spaces","authors":"Sruthy Poulose;Yara Alvarez-Braña;Lourdes Basabel-Desmonts;Fernando Benito-Lopez;John Michael David Coey","doi":"10.1109/LMAG.2023.3262976","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3262976","url":null,"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 mm\u0000<sup>2</sup>\u0000 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\u0000<inline-formula><tex-math>$cdot$</tex-math></inline-formula>\u0000m\u0000<sup>−2</sup>\u0000<inline-formula><tex-math>$cdot$</tex-math></inline-formula>\u0000h\u0000<sup>−1</sup>\u0000 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 \u0000<italic>ortho</i>\u0000 and \u0000<italic>para</i>\u0000 nuclear isomers of water vapor, which behave as independent gasses. The \u0000<italic>ortho:para</i>\u0000 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.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/iel7/5165412/10018138/10092455.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67763008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Mössbauer spectroscopy (MS) study was performed on the superparamagnetic commercially available magnetic fluid, Resovist, with temperatures varying between room temperature and 2.6 K. Two samples were prepared for MS study, one dried specimen and the other frozen. At the lowest temperature of 2.6 K, the spectrum was characteristic of maghemite, and superparamagnetic relaxation was observed with increasing temperature. On the spectrum recorded at 250 K, fitting was performed using the three components in the Blume–Tjon two-state magnetic relaxation model, which resulted in relaxation times of $3.8 times 10^{-8}$ , $1.7 times 10^{-8}$ , and $6.4 times 10^{-10}$ s for the three components.
{"title":"Magnetic Relaxation of Superparamagnetic Fe Oxide Particles Studied With Mössbauer Spectroscopy","authors":"Eiji Kita;Reisho Onodera;Mikio Kishimoto;Hideto Yanagihara","doi":"10.1109/LMAG.2023.3264115","DOIUrl":"https://doi.org/10.1109/LMAG.2023.3264115","url":null,"abstract":"A Mössbauer spectroscopy (MS) study was performed on the superparamagnetic commercially available magnetic fluid, Resovist, with temperatures varying between room temperature and 2.6 K. Two samples were prepared for MS study, one dried specimen and the other frozen. At the lowest temperature of 2.6 K, the spectrum was characteristic of maghemite, and superparamagnetic relaxation was observed with increasing temperature. On the spectrum recorded at 250 K, fitting was performed using the three components in the Blume–Tjon two-state magnetic relaxation model, which resulted in relaxation times of \u0000<inline-formula><tex-math>$3.8 times 10^{-8}$</tex-math></inline-formula>\u0000, \u0000<inline-formula><tex-math>$1.7 times 10^{-8}$</tex-math></inline-formula>\u0000, and \u0000<inline-formula><tex-math>$6.4 times 10^{-10}$</tex-math></inline-formula>\u0000 s for the three components.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2023-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67919309","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 : 2023-03-30DOI: 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}
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