Article
Physics, Applied
A. Roman, A. Lopez Pedroso, K. Bouzehouane, J. E. Gomez, A. Butera, M. H. Aguirre, M. Medeiros Soares, C. Garcia, L. B. Steren
Summary: The competition between shape and perpendicular magnetic anisotropies in magnetic thin films leads to unconventional magnetic behaviors. In ferromagnetic thin films, the out-of-plane component of magnetic anisotropy can induce a transition from planar to stripe-like magnetic domains above a critical thickness, tc. This article presents a detailed study of the magnetization switching mechanism in FePt thin films where this phenomenon is observed. Micromagnetic simulations and experiments show that below tc, the reversal mechanism is well described by the two-phase model, while above this thickness, the magnetization within each stripe reverses through coherent rotation. The out-of-plane component and its temperature dependence of the magnetic anisotropy were also analyzed, indicating that substrate-induced strains are responsible for the abnormal coercive field behavior observed for FePt films with t > tc.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Multidisciplinary Sciences
Chengchao Xu, B. S. D. Ch. S. Varaprasad, David E. Laughlin, Jian-Gang Zhu
Summary: In this paper, an experimental study of L1(0)-FePt granular films with crystalline boron nitride (BN) grain boundary materials for heat assisted magnetic recording (HAMR) is presented. It is found that RF substrate bias induces the formation of hexagonal boron nitride (h-BN) nanosheets in grain boundaries, facilitating the growth of FePt grains during sputtering. The resulting core-shell FePt-(h-BN) nanostructures show high promise for HAMR application, with high thermal stability and excellent magnetic properties.
SCIENTIFIC REPORTS
(2023)
Article
Engineering, Multidisciplinary
Kaifeng Dong, Chao Sun, Laizhe Zhu, Yiyi Jiao, Ying Tao, Xin Hu, Ruofan Li, Shuai Zhang, Zhe Guo, Shijiang Luo, Xiaofei Yang, Shaoping Li, Long You
Summary: In this study, current-induced partial magnetization-based switching was achieved in single-layer L1(0) FePt with a high spin-orbit torque (SOT) efficiency. The SOT in FePt films was found to be influenced by the structural inversion asymmetry and microstructure evolution induced by lattice mismatch.
Article
Physics, Applied
Guo-liang Yu, Tai-min Cheng, Xin-xin Zhang
Summary: The magnetic, elastic, and dynamical properties of L1(0)-type FePt alloy under high pressure were studied using first-principles calculations. The critical pressure for the collapse of ferromagnetism was identified as 96.7 GPa, with the alloy remaining mechanically stable up to 120 GPa. Ductility showed little change with pressure below the critical value, while the elastic anisotropy increased. However, both ductility and elastic anisotropy experienced a sudden decrease beyond the critical pressure. The alloy exhibited dynamical stability under ambient and high pressures, with the stability attributed to spontaneous magnetization below the critical pressure. The anisotropy of the phonon density of states under high pressure was evaluated in detail, and it was found to be almost independent of pressure.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
S. Sawada, K. Okai, H. Fukui, R. Takahashi, N. Ishimatsu, H. Maruyama, N. Kawamura, S. Kawaguchi, N. Hirao, T. Seki, K. Takanashi, S. Ohmura, H. Wadati
Summary: We investigated the relationship between lattice constant and magnetism of L1(0)-ordered FePt under high pressure using first-principles calculations and synchrotron x-ray measurements. Our calculations showed a local maximum of the c/a ratio at around 20 GPa, and the Pt magnetic moment remained almost unchanged until around 60 GPa before sharply decreasing. Experimentally, we verified the local maximum of c/a at around 20 GPa through powder x-ray diffraction and observed no significant change in Pt magnetic moment up to around 20 GPa using x-ray magnetic circular dichroism at the Pt L edge.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Tatsuya Yamamoto, Takayuki Nozaki, Kay Yakushiji, Shingo Tamaru, Hitoshi Kubota, Akio Fukushima, Shinji Yuasa
Summary: The study shows that Ta layer in MgO/Ta/CoFeB/MgO junctions can enhance the PMA of magnetic films and eliminate the diffusion of Ta, leading to superior thermal stability and the release of VCMA effect. In addition, the Co-Fe compositional variation in CoFeB layer associated with Ta insertion is related to the changes in PMA and VCMA.
Article
Materials Science, Multidisciplinary
Van Quang Nguyen, Byung-Hyuk Jun, Young-Bum Chun, June Hyuk Lee
Summary: In this work, high-quality ordered L10-FeNi films were successfully fabricated by using a two-step codeposition method below 250°C on Al2O3 (0001) substrate through molecular beam epitaxy. The obtained film exhibited high uniaxial magnetic anisotropy constant and can be considered as a potential rare-earth-free permanent magnet material for the next generation.
Article
Engineering, Electrical & Electronic
Takashi Saito, Kim Kong Tham, Ryosuke Kushibiki, Tomoyuki Ogawa, Shin Saito
Summary: The study on the magnetic anisotropy of L1(0)-typed FePt granular media reveals that the K-u(perpendicular)exp is strongly correlated with grain diameter and degree of order, while not significantly correlated with the melting point of grain boundary materials.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Physics, Applied
He Bai, Z. Z. Zhu, J. T. Ke, Gang Li, Jian Su, Ying Zhang, Tao Zhu, J. W. Cai
Summary: We demonstrate that substituted rare-earth iron garnets can exhibit perpendicular magnetic anisotropy (PMA) and have the potential to be used in spintronics devices with tunable PMA. By analyzing the structural and transport properties of the films, we show that the PMA field can be tuned within a large range while the switching current density remains nearly constant.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Applied
J. D. Miller, H. J. Trodahl, M. Al Khalfioui, S. Vezian, B. J. Ruck
Summary: A unique bulk-origin perpendicular magnetic anisotropy (PMA) was found in thin films of the cubic ferromagnetic semiconductor GdxSm1-xN. The films exhibited out-of-plane remanence reaching 80% of the saturation magnetization in films with up to 30% Gd, as indicated by in-vs-out-of-plane magnetic hysteresis. Anomalous Hall effect data showed that the conduction-band spin imbalance retained 100% remanence, maintaining half-metallic conduction even when the out-of-plane applied field was reduced to zero, in contrast to the 80% magnetization remanence. The occurrence of PMA in this cubic material was discussed as stabilized by a mixture of two in-plane crystal orientations in the epitaxial (111)-oriented films.
APPLIED PHYSICS LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Qi Liu, Pengfei Liu, Xiaowen Li, Sixia Hu, Yuanmin Zhu, Cai Jin, Wenqiao Han, Yanjiang Ji, Zedong Xu, Songbai Hu, Mao Ye, Lang Chen
Summary: By designing and fabricating manganite-based magnetic tunnel junctions, we achieved perpendicular tunneling and observed spin-dependent tunneling behavior. The dominant role of direct tunneling was observed in the low bias region, while it was associated with thermionic emission in the high bias region.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Young Chan Won, Jae-Pyoung Ahn, Sang Ho Lim
Summary: This study investigated the perpendicular magnetic anisotropy (PMA) and microstructure of Pt/Co/AlN stacks. It was found that the magnetic moment significantly increased after annealing, leading to strong PMA. The effective PMA energy densities were 2.28 and 1.96 x 10(7) erg/cm(3) after annealing at 300 and 400 degrees C, respectively. High-resolution cross-sectional transmission electron microscopy confirmed the presence of strong PMA.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Multidisciplinary
Maria Ameziane, Rhodri Mansell, Ville Havu, Patrick Rinke, Sebastiaan van Dijken
Summary: This study demonstrates the reversible voltage-controlled switching between perpendicular and in-plane magnetization states in a Co-Pt bilayer using solid-state lithium-ion battery technology. Due to the small size and high mobility of lithium ions, small voltages produce an exceptionally high magnetoelectric coupling efficiency. The magnetic switching effect is attributed to the modulation of spin-orbit coupling at the Co-Pt interface when lithium ions migrate between a lithium storage layer and the magnetic interface across a solid-state electrolyte.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Mengchao Li, Huali Yang, Yali Xie, Kai Huang, Lili Pan, Wei Tang, Xilai Bao, Yumeng Yang, Jie Sun, Xinming Wang, Shenglei Che, Run-Wei Li
Summary: The magnetic properties of flexible magnetic films are sensitive to mechanical stress due to magnetoelastic coupling, which affects the performance of flexible magnetoelectronic devices. We demonstrate that stacking different materials in multilayers can enhance the stress stability of the magnetic properties. The strength of magnetoelastic anisotropy and the initial effective magnetic anisotropy play significant roles in determining the stress stability of the film.
Article
Chemistry, Physical
Qingwang Bai, Jie Jiang, Bin Guo, Wentian Cao, Xianwu Xiu, Shuyun Wang
Summary: Increasing the interfaces of heavy metal ferromagnetic (HM/FM) can enhance the perpendicular magnetic anisotropy (PMA) of multilayers. The addition of more Pd/CMS interfaces can improve PMA and magnetic saturation (M-s), leading to reduced energy consumption in magnetic recording writing.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Nanoscience & Nanotechnology
Iduru Shigeta, Shuta Oku, Takahide Kubota, Shojiro Kimura, Takeshi Seki, Bunju Shinozaki, Satoshi Awaji, Koki Takanashi, Masahiko Hiroi
Summary: Superconducting properties of NbN/CMS films were investigated. The upper critical field decreased with increasing CMS thickness, while the superconducting transition temperature had a minimum value at a thickness of around 5 nm. The experimental results suggest that the superconductivity of the NbN layer is affected by the interaction between the NbN and the CMS layers.
Article
Physics, Applied
Hiroto Masuda, Yuta Yamane, Takeshi Seki, Klaus Raab, Takaaki Dohi, Rajkumar Modak, Ken-ichi Uchida, Jun'ichi Ieda, Mathias Klaui, Koki Takanashi
Summary: We report current-induced magnetization switching in Pt/Co/Ir/Co/Pt multilayers with different Ir layer thicknesses. The domain structures formed during switching vary depending on the magnetization alignment, either ferromagnetic or antiferromagnetic. Numerical calculations reveal the switching dynamics triggered by dual spin-orbit torques for both cases. Our findings deepen the understanding of the switching mechanism in magnetic multilayers and provide a pathway for designing spintronic devices with more efficient spin-orbit torque switching.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
S. Sawada, K. Okai, H. Fukui, R. Takahashi, N. Ishimatsu, H. Maruyama, N. Kawamura, S. Kawaguchi, N. Hirao, T. Seki, K. Takanashi, S. Ohmura, H. Wadati
Summary: We investigated the relationship between lattice constant and magnetism of L1(0)-ordered FePt under high pressure using first-principles calculations and synchrotron x-ray measurements. Our calculations showed a local maximum of the c/a ratio at around 20 GPa, and the Pt magnetic moment remained almost unchanged until around 60 GPa before sharply decreasing. Experimentally, we verified the local maximum of c/a at around 20 GPa through powder x-ray diffraction and observed no significant change in Pt magnetic moment up to around 20 GPa using x-ray magnetic circular dichroism at the Pt L edge.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Yoji Kunihashi, Yasushi Shinohara, Sho Hasegawa, Hiroyuki Nishinaka, Masahiro Yoshimoto, Katsuya Oguri, Hideki Gotoh, Makoto Kohda, Junsaku Nitta, Haruki Sanada
Summary: The incorporation of heavy atoms into semiconductor heterostructures can enhance the spin-orbit interaction of carriers moving in two-dimensional channels. In this study, we investigated the strength of spin-orbit interaction in a GaAsBi channel. Our findings showed the existence of Rashba-type spin-orbit effective magnetic fields experienced by the photo-injected spins diffusing in the GaAsBi layer.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Zhenyu Zhou, William Frost, David C. Lloyd, Takeshi Seki, Takahide Kubota, Rafael Ramos, Eiji Saitoh, Koki Takanashi, Atsufumi Hirohata
Summary: Recent development in neuromorphic computation allows for low power, highly efficient calculations surpassing conventional von Neumann computation. Realistic synaptic operation requires potentiation through reducing electrical resistance of artificial synapses. A recent study demonstrated current-induced crystallisation in a magnetoresistive junction with a ferromagnetic Heusler alloy, which can be extended to epitaxially-grown Heusler alloys for realistic synaptic computation.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Physics, Multidisciplinary
Jun Ishihara, Takachika Mori, Takuya Suzuki, Sota Sato, Ken Morita, Makoto Kohda, Yuzo Ohno, Kensuke Miyajima
Summary: This study transfers the spatially variant polarization of topologically structured light to the spatial spin texture in a semiconductor quantum well. By controlling the spatial wave number of the excited spin mode, the generated spin texture efficiently evolves into a helical spin wave pattern.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Applied
Tariq F. Alhuwaymel, Takahide Kubota, Jun-Young Kim, Koki Takanashi, Atsufumi Hirohata
Summary: Researchers have developed a new technique to directly measure the half-metallic bandgap by using circularly polarized infrared light. This technique can provide a simple evaluation of the properties of a half-metallic film.
Article
Physics, Applied
Takumi Yamazaki, Takeshi Seki, Takahide Kubota, Koki Takanashi
Summary: This study reports the effect of epitaxial growth on the spin current transmission of NiO films. Two series of samples, including epitaxial and polycrystalline NiO, were prepared using different deposition conditions. The spin current transmission of NiO was evaluated using thermo-spin effects. Epitaxial NiO exhibited a non-monotonic behavior in the thickness dependence of spin current transmission, revealing the presence of multiple spin transport mechanisms.
APPLIED PHYSICS EXPRESS
(2023)
Article
Physics, Applied
Makoto Kohda, Takeshi Seki, Yasushi Yuminaka, Tetsuya Uemura, Keito Kikuchi, Gian Salis
Summary: This article discusses the differences between waves and particle properties, as well as their applications in data processing and storage. It introduces the information theory of wave-parallel computing and the fundamental properties needed for wave-based information carriers. The potential of electron spin waves and magnons as information carriers for processing and storage is examined. The interconversion among light helicity, electron spin waves, and magnons is also discussed.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Ryuji Atsumi, Junichi Shiogai, Takumi Yamazaki, Takeshi Seki, Kohei Ueda, Jobu Matsuno
Summary: Manganite perovskites have emerging physical properties of strongly-correlated electrons, and using the epitaxial lift-off technique can enhance the saturation magnetization and ferromagnetic transition temperature. They are suitable for flexible electronic applications.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Multidisciplinary Sciences
A. Nabialek, O. M. Chumak, P. Aleshkevych, J. Z. Domagala, A. Pacewicz, B. Salski, J. Krupka, T. Seki, K. Takanashi, L. T. Baczewski, H. Szymczak
Summary: In this study, the perpendicular magnetocrystalline anisotropy, magnetoelastic properties, and Gilbert damping factor in Co2Fe0.4Mn0.6Si thin films were found to be dependent on the magnetic layer thickness and could be tuned by the addition of an Ag buffer layer. The tetragonal distortion of the magnetic layer increased with decreasing thickness, and the character of this distortion changed from tensile to compressive in the plane of the film after the application of an additional Ag buffer layer. There was a correlation between the tetragonal distortion and perpendicular magnetocrystalline anisotropy, but the observed magnitude of the tetragonal distortion seems to be too small to fully explain the experimentally found large magnitude of the perpendicular magnetocrystalline anisotropy in most samples.
SCIENTIFIC REPORTS
(2023)
Article
Energy & Fuels
Asaya Fujita, Kaoru Imaizumi
Summary: The magnetocaloric effect (MCE) in La1-zR(z)(Fe0.89-xMn(x)Si-0.11)(13)H(y)(max)(R = Ce and Pr) is confirmed to be influenced by alloying recipes and fundamental physics. The Ce-doped specimen with z = 0.3 & x = 0.017 exhibits a peaky isothermal entropy change & UDelta;S(M) profile with a maximum value of 20 J kg(-1) K at 285 K and a field change of 0.8 T. In contrast, the Pr-doped specimen shows an enlarged field dependence and diminished hysteresis, resulting in an adiabatic temperature change & UDelta;T(ad) of 2.7 K at 289 K and a field change of 0.8 T.
JOURNAL OF PHYSICS-ENERGY
(2023)
Article
Physics, Multidisciplinary
Takeshi Seki, Yong-Chang Lau, Junya Ikeda, Kohei Fujiwara, Akihiro Ozawa, Satoshi Iihama, Kentaro Nomura, Atsushi Tsukazaki
Summary: In this paper, the temperature dependence of conversion between charge current and spin current for CSS thin film was investigated. The spin-torque ferromagnetic resonance (ST-FMR) measurement was performed on a CSS/Cu/CoFeB trilayer structure. It was found that both the anisotropic magnetoresistance (AMR) and the giant magnetoresistance (GMR) contribute to the ST-FMR signal below the ferromagnetic phase transition temperature (TC). The results also showed an increase in spin-charge conversion efficiency at T < TC.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Yong-Chang Lau, Junya Ikeda, Kohei Fujiwara, Akihiro Ozawa, Jiaxin Zheng, Takeshi Seki, Kentaro Nomura, Liang Du, Quansheng Wu, Atsushi Tsukazaki, Koki Takanashi
Summary: Magnetic Weyl semimetals exhibit chiral Weyl node pairs and large intrinsic anomalous Hall effect. This study demonstrates the potential of Dirac nodes in paramagnetic state for efficient spin current generation at room temperature via the spin Hall effect.
Review
Computer Science, Information Systems
Atsufumi Hirohata, David C. Lloyd, Takahide Kubota, Takeshi Seki, Koki Takanashi, Hiroaki Sukegawa, Zhenchao Wen, Seiji Mitani, Hiroki Koizumi
Summary: Spintronic devices show promise in replacing nanoelectronic memories and sensors due to their efficiency and scalability. To achieve further miniaturization, new materials development is necessary, such as increasing spin polarization or using antiferromagnets. Recent studies have found interesting properties in antiferromagnetic materials, such as 100% spin-polarized current and topological effects. This review summarizes the recent development of three types of antiferromagnets and discusses their potential for device applications.
