Pub Date : 2023-01-01DOI: 10.1109/LMAG.2024.3379164
{"title":"TechRxiv: Share Your Preprint Research with the World!","authors":"","doi":"10.1109/LMAG.2024.3379164","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3379164","url":null,"abstract":"","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-1"},"PeriodicalIF":1.2,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10477288","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140181515","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 : 2022-12-23DOI: 10.1109/LMAG.2022.3231819
Haochen Zhang;Yi Sun;Zhongzhou Du;Teruyoshi Sasayama;Takashi Yoshida
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.
{"title":"Numerical Study on the Magnetization Characteristics of Chainlike Magnetic Nanoparticles","authors":"Haochen Zhang;Yi Sun;Zhongzhou Du;Teruyoshi Sasayama;Takashi Yoshida","doi":"10.1109/LMAG.2022.3231819","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3231819","url":null,"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.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"14 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67762119","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 presents a novel and compact structure that integrates silicon-carbide (SiC) Schottky diodes within a high-frequency transformer (HFT). The proposed structure would reduce the volume of a power converter and, in turn, the system to which it is applied. It would also greatly reduce the leakage inductances of an HFT as well as the inductive electromagnetic interference to surrounding components and devices. A prototype HFT shaped much like a torus is designed for integration with SiC Schottky diodes. The three-dimensional finite-element method simulation technique is used to design and analyze the magnetic structure of the HFT including the space reserved for the SiC Schottky diodes. Experimental results are presented for both the HFT as a separate component and as a system integrated with SiC Schottky diodes.
{"title":"Integration of Novel High-Frequency Transformer With Silicon-Carbide Schottky Diodes","authors":"Weichong Yao;Junwei Lu;Andrew Seagar;Feifei Bai;Foad Taghizadeh","doi":"10.1109/LMAG.2022.3229230","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3229230","url":null,"abstract":"This letter presents a novel and compact structure that integrates silicon-carbide (SiC) Schottky diodes within a high-frequency transformer (HFT). The proposed structure would reduce the volume of a power converter and, in turn, the system to which it is applied. It would also greatly reduce the leakage inductances of an HFT as well as the inductive electromagnetic interference to surrounding components and devices. A prototype HFT shaped much like a torus is designed for integration with SiC Schottky diodes. The three-dimensional finite-element method simulation technique is used to design and analyze the magnetic structure of the HFT including the space reserved for the SiC Schottky diodes. Experimental results are presented for both the HFT as a separate component and as a system integrated with SiC Schottky diodes.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"13 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2022-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67902597","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 : 2022-12-13DOI: 10.1109/LMAG.2022.3225742
Hans T. Nembach;Justin M. Shaw;Chloe S. Taylor;Daniel B. Gopman
Ultrathin Ta/CoFeB/Pt trilayer structures are relevant to a wide range of spintronic applications, from magnetic tunnel junctions to skyrmionics devices. Controlling the perpendicular magnetic anisotropy, Gilbert damping, and Dzyaloshinskii–Moriya interaction (DMI) in the CoFeB layer is key for these applications. We examine the role of sputter gas composition during the Pt overlayer deposition of a Ta/CoFeB/Pt trilayer in Ar, Kr, and Xe working gas environments during direct current magnetron sputtering. The decreasing density of the Pt layer (from 21 to 15 g/cm 3 ) was apparent in specular X-ray reflectivity measurements of the trilayer films when increasing the molecular weight of the sputtering gas from Ar to Kr to Xe. Significant effects on the Gilbert damping and the interfacial DMI energy were observed, with increases in the damping from 0.037(1) to 0.042(1) to 0.048(1), and reductions in the interfacial DMI from 0.47(4) mJ/m 2 to 0.45(5) mJ/m 2 to 0.39(4) mJ/m 2 . The ability to control the perpendicular magnetization and DMI strength of these materials through judicious interfacial control is a means toward magnetic devices with better stability at smaller lateral dimensions, the key to device scaling for spintronic device arrays.
{"title":"Effect of Gas Composition During Pt Sputtering on Structural and Magnetic Properties of CoFeB Thin Films","authors":"Hans T. Nembach;Justin M. Shaw;Chloe S. Taylor;Daniel B. Gopman","doi":"10.1109/LMAG.2022.3225742","DOIUrl":"10.1109/LMAG.2022.3225742","url":null,"abstract":"Ultrathin Ta/CoFeB/Pt trilayer structures are relevant to a wide range of spintronic applications, from magnetic tunnel junctions to skyrmionics devices. Controlling the perpendicular magnetic anisotropy, Gilbert damping, and Dzyaloshinskii–Moriya interaction (DMI) in the CoFeB layer is key for these applications. We examine the role of sputter gas composition during the Pt overlayer deposition of a Ta/CoFeB/Pt trilayer in Ar, Kr, and Xe working gas environments during direct current magnetron sputtering. The decreasing density of the Pt layer (from 21 to 15 g/cm\u0000<sup>3</sup>\u0000) was apparent in specular X-ray reflectivity measurements of the trilayer films when increasing the molecular weight of the sputtering gas from Ar to Kr to Xe. Significant effects on the Gilbert damping and the interfacial DMI energy were observed, with increases in the damping from 0.037(1) to 0.042(1) to 0.048(1), and reductions in the interfacial DMI from 0.47(4) mJ/m\u0000<sup>2</sup>\u0000 to 0.45(5) mJ/m\u0000<sup>2</sup>\u0000 to 0.39(4) mJ/m\u0000<sup>2</sup>\u0000. The ability to control the perpendicular magnetization and DMI strength of these materials through judicious interfacial control is a means toward magnetic devices with better stability at smaller lateral dimensions, the key to device scaling for spintronic device arrays.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"13 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2022-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10161395/pdf/nihms-1880596.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9437969","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 : 2022-12-05DOI: 10.1109/LMAG.2022.3226918
B. P. Alho;P. O. Ribeiro;R. S. de Oliveira;V. S. R. de Sousa;E. P. Nóbrega;B. C. Margato;J. M. N. da Silva;P. J. von Ranke
Antiferromagnetic compounds are known in the literature to present the inverse magnetocaloric effect (MCE). This effect is characterized by the negative adiabatic temperature change $Delta {T}_S$ of an antiferromagnetic material when submitted to an applied magnetic field. In an isothermal process, a positive entropy change $Delta {S}_T$ is also expected. More recently, the anisotropic character of antiferromagnetic compounds, due to spin-flop and spin-flip transitions, has been pointed out, highlighting the applicability of the antiferromagnetic compounds in a rotary magnetocaloric device. In this work, we systematically investigated a mean-field model that describes the antiferromagnetic behavior of materials in a multisublattice approach. Our model includes the nearest and next-nearest neighbor exchange interaction, the Zeeman effect, and uniaxial anisotropy energy. We investigated the effect of anisotropy on the spin-flop and spin-flip transitions on the usual and anisotropic MCE. We also demonstrated and verified an area rule for $ - {rm{Delta }}{S}_T$ versus T curves that can be used on compounds where the saturation magnetization is magnetic field dependent.
{"title":"Mean-Field Modeling of Magnetocaloric Effect of Antiferromagnetic Compounds","authors":"B. P. Alho;P. O. Ribeiro;R. S. de Oliveira;V. S. R. de Sousa;E. P. Nóbrega;B. C. Margato;J. M. N. da Silva;P. J. von Ranke","doi":"10.1109/LMAG.2022.3226918","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3226918","url":null,"abstract":"Antiferromagnetic compounds are known in the literature to present the inverse magnetocaloric effect (MCE). This effect is characterized by the negative adiabatic temperature change \u0000<inline-formula><tex-math>$Delta {T}_S$</tex-math></inline-formula>\u0000 of an antiferromagnetic material when submitted to an applied magnetic field. In an isothermal process, a positive entropy change \u0000<inline-formula><tex-math>$Delta {S}_T$</tex-math></inline-formula>\u0000 is also expected. More recently, the anisotropic character of antiferromagnetic compounds, due to spin-flop and spin-flip transitions, has been pointed out, highlighting the applicability of the antiferromagnetic compounds in a rotary magnetocaloric device. In this work, we systematically investigated a mean-field model that describes the antiferromagnetic behavior of materials in a multisublattice approach. Our model includes the nearest and next-nearest neighbor exchange interaction, the Zeeman effect, and uniaxial anisotropy energy. We investigated the effect of anisotropy on the spin-flop and spin-flip transitions on the usual and anisotropic MCE. We also demonstrated and verified an area rule for \u0000<inline-formula><tex-math>$ - {rm{Delta }}{S}_T$</tex-math></inline-formula>\u0000 versus \u0000<italic>T</i>\u0000 curves that can be used on compounds where the saturation magnetization is magnetic field dependent.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"13 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2022-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741217","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 : 2022-12-05DOI: 10.1109/LMAG.2022.3226656
Sergey V. Kolesnikov;Ekaterina S. Sapronova
The spontaneous magnetization reversal of the finite-length Co chains on Pt(664) surface is investigated in the framework of the classical effective theory. The effective theory includes the Heisenberg exchange interaction, magnetic anisotropy energy, Dzyaloshinskii–Moriya interaction (DMI), and dipole–dipole interaction. The geodesic-nudged elastic band method is employed for calculations of the energy barriers for magnetization reversal of the finite-length Co chains. The calculation of the spontaneous magnetization reversal time shows that the dipole–dipole interaction can be neglected at a temperatures higher than 10.9 K. DMI can be neglected at temperatures higher than 60.2 K. This means that DMI can significantly influence the magnetization reversal process at low temperatures and should be taken into account.
{"title":"Influence of Dzyaloshinskii–Moriya and Dipole–Dipole Interactions on Spontaneous Magnetization Reversal Time of Finite-Length Co Chains on Pt(664) Surfaces","authors":"Sergey V. Kolesnikov;Ekaterina S. Sapronova","doi":"10.1109/LMAG.2022.3226656","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3226656","url":null,"abstract":"The spontaneous magnetization reversal of the finite-length Co chains on Pt(664) surface is investigated in the framework of the classical effective theory. The effective theory includes the Heisenberg exchange interaction, magnetic anisotropy energy, Dzyaloshinskii–Moriya interaction (DMI), and dipole–dipole interaction. The geodesic-nudged elastic band method is employed for calculations of the energy barriers for magnetization reversal of the finite-length Co chains. The calculation of the spontaneous magnetization reversal time shows that the dipole–dipole interaction can be neglected at a temperatures higher than 10.9 K. DMI can be neglected at temperatures higher than 60.2 K. This means that DMI can significantly influence the magnetization reversal process at low temperatures and should be taken into account.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"13 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2022-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741218","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 : 2022-12-02DOI: 10.1109/LMAG.2022.3226031
Brooke C. McGoldrick;Jonathan Z. Sun
Probabilistic bits (p-bits) based on magnetic tunnel junctions are of recent interest in probabilistic and neuromorphic computing architectures based on their small size, high operating speeds, and truly stochastic nature. In practical systems, the output probability of the bit can be tuned by an applied current, which is generally characterized by a quasi-static tuning curve. In this letter, we instead focus on the finite time it takes the p-bit's probabilistic distribution to respond to an applied bias current. We find that this settling time is in the range of hundreds of picoseconds for a typical junction, and is highly dependent on various parameters, including the device size, material properties, and magnitude of the applied current. These results provide a baseline understanding of the dynamic properties of a nanomagnetic p-bit's probability distribution, which is helpful for p-bit-related system architecture discussions.
{"title":"Settling Time of Current-Tunable Probabilistic Bit's Distribution","authors":"Brooke C. McGoldrick;Jonathan Z. Sun","doi":"10.1109/LMAG.2022.3226031","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3226031","url":null,"abstract":"Probabilistic bits (p-bits) based on magnetic tunnel junctions are of recent interest in probabilistic and neuromorphic computing architectures based on their small size, high operating speeds, and truly stochastic nature. In practical systems, the output probability of the bit can be tuned by an applied current, which is generally characterized by a quasi-static tuning curve. In this letter, we instead focus on the finite time it takes the p-bit's probabilistic distribution to respond to an applied bias current. We find that this settling time is in the range of hundreds of picoseconds for a typical junction, and is highly dependent on various parameters, including the device size, material properties, and magnitude of the applied current. These results provide a baseline understanding of the dynamic properties of a nanomagnetic p-bit's probability distribution, which is helpful for p-bit-related system architecture discussions.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"13 ","pages":"1-4"},"PeriodicalIF":1.2,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741588","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}
Wearable and implantable devices (WIDs) come with several separate blocks such as preprocessing units, memory, and data transmission blocks. Hence, in this letter, we present the concept of memory and communication-in-logic (MCL) using a magnetic tunnel junction (MTJ). Here, MTJ is presented as a memory device as well as an oscillator for communication purposes. Vortex-based spin-torque nanooscillators (V-STNO) and precessional STNOs (P-STNO) generate a microwave frequency range (a few hundred MHz to a few GHz) wherein the frequency readout technique using the spin-torque diode is implemented for memory read function. In this work, a 300 nm nanodisk V-STNO generates 296 and 312 MHz frequency for two states of chirality (a characteristic of magnetic vortex), respectively. These different frequencies can be sensed for a bit “0”/ “1” read out through which the data from WIDs can be transmitted in a more energy- and area-efficient way. The output power emission is 3.22 and 1.76 µW for bit “1” and “0,” respectively, for V-STNO, which is three orders of magnitude larger than that of P-STNO. Finally, we demonstrate that V-STNO can transmit data up to 10 m in the air medium, which is much longer than P-STNO (0.24 m).
{"title":"Memory and Communication-in-Logic Using Vortex and Precessional Oscillations in a Magnetic Tunnel Junction","authors":"Sonal Shreya;Milad Zamani;Yaseer Rezaeiyan;Hamdam Ghanatian;Tim Böhnert;Alex S. Jenkins;Ricardo Ferreira;Hooman Farkhani;Farshad Moradi","doi":"10.1109/LMAG.2022.3224676","DOIUrl":"https://doi.org/10.1109/LMAG.2022.3224676","url":null,"abstract":"Wearable and implantable devices (WIDs) come with several separate blocks such as preprocessing units, memory, and data transmission blocks. Hence, in this letter, we present the concept of memory and communication-in-logic (MCL) using a magnetic tunnel junction (MTJ). Here, MTJ is presented as a memory device as well as an oscillator for communication purposes. Vortex-based spin-torque nanooscillators (V-STNO) and precessional STNOs (P-STNO) generate a microwave frequency range (a few hundred MHz to a few GHz) wherein the frequency readout technique using the spin-torque diode is implemented for memory read function. In this work, a 300 nm nanodisk V-STNO generates 296 and 312 MHz frequency for two states of chirality (a characteristic of magnetic vortex), respectively. These different frequencies can be sensed for a bit “0”/ “1” read out through which the data from WIDs can be transmitted in a more energy- and area-efficient way. The output power emission is 3.22 and 1.76 µW for bit “1” and “0,” respectively, for V-STNO, which is three orders of magnitude larger than that of P-STNO. Finally, we demonstrate that V-STNO can transmit data up to 10 m in the air medium, which is much longer than P-STNO (0.24 m).","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"13 ","pages":"1-5"},"PeriodicalIF":1.2,"publicationDate":"2022-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67741587","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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