Article
Multidisciplinary Sciences
Xin Yu Zheng, Sanyum Channa, Lauren J. Riddiford, Jacob J. Wisser, Krishnamurthy Mahalingam, Cynthia T. Bowers, Michael E. McConney, Alpha T. N'Diaye, Arturas Vailionis, Egecan Cogulu, Haowen Ren, Zbigniew Galazka, Andrew D. Kent, Yuri Suzuki
Summary: This study introduces a ferromagnetic insulator spinel, Li0.5Al1.0Fe1.5O4 (LAFO), with low magnetic damping, perpendicular magnetic anisotropy, and no magnetic dead layer. By integrating these LAFO films with epitaxial Pt spin source layers, record low magnetization switching currents and high spin-orbit torque efficiencies are achieved.
NATURE COMMUNICATIONS
(2023)
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
Nanoscience & Nanotechnology
Zeliang Ren, Bin Lao, Xuan Zheng, Lei Liao, Zengxing Lu, Sheng Li, Yongjie Yang, Bingshan Cao, Lijie Wen, Kenan Zhao, Lifen Wang, Xuedong Bai, Xianfeng Hao, Zhaoliang Liao, Zhiming Wang, Run-Wei Li
Summary: This study reports the epitaxial growth of magnetic insulator films with strong perpendicular magnetic anisotropy and their potential application in spintronic devices. The films exhibit high crystalline quality, ferrimagnetic and insulating transport characteristics, as well as pronounced spin Hall magnetoresistance and spin Hall-like anomalous Hall effect in constructed heterostructures.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Y. Q. Guo, H. Bai, Q. R. Cui, L. M. Wang, Y. C. Zhao, X. Z. Zhan, T. Zhu, H. X. Yang, Y. Gao, C. Q. Hu, S. P. Shen, C. L. He, S. G. Wang
Summary: The effect of vacuum annealing on the perpendicular magnetic anisotropy of MgO/CoFeB/VV stacks was studied, showing that the PMA can be well maintained at 590 degrees C. Furthermore, there was significant segregation of Co and Fe atoms at the CoFeB/W interface after annealing at this temperature.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
A. Talapatra, J. Arout Chelvane, J. Mohanty
Summary: The research reveals that high ion irradiation doses lead to changes in the magnetic properties of amorphous Tb-Fe-Co films, and the form of magnetic domain modification transitions from rapid domain wall motion to nucleation and propagation of reverse domains.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Multidisciplinary
Bo-Yao Wang, Tzu-Hsin Li, Bo -Xiang Liao, Chung-Hsuan Hsiao, Li-Han Chang, Ming-Shian Tsai, Tzu-Hung Chuang, Der-Hsin Wei
Summary: This study explores the use of antiferromagnetic (AFM) thin films to manipulate perpendicular magnetic anisotropy (PMA) in ferromagnetic (FM) thin films. By adjusting the AFM layer in a composite material, long-range AFM ordering in adjacent AFM materials can be enhanced, and control over their spin structure can be exerted, resulting in the induction of PMA in neighboring FM films.
Article
Materials Science, Multidisciplinary
Ashok Pokhrel, Bhuwan Nepal, Upama Karki, Arjun Sapkota, Anish Rai, Sara Bey, Tim Mewes, Claudia Mewes
Summary: This article investigates the influence of layer dependent second-order perpendicular anisotropy on higher-order anisotropies in thin films using a macrospin model. The study finds that the origin of the fourth-order anisotropy is linked to the layer-wise variation of magnetization direction, resulting in a dependence on field strength and exchange stiffness. Furthermore, it is observed that the apparent fourth-order anisotropy increases with decrease in exchange stiffness.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Nanoscience & Nanotechnology
Dima Sadek, Daya S. Dhungana, Roland Coratger, Corentin Durand, Arnaud Proietti, Quentin Gravelier, Benjamin Reig, Emmanuelle Daran, Pier Francesco Fazzini, Fuccio Cristiano, Alexandre Arnoult, Sebastien R. Plissard
Summary: The bismuth-antimony alloy is the first reported 3D topological insulator with promising potential for spintronic applications. This work successfully demonstrates the integration of high-quality rhombohedral BiSb topological insulators on a GaAs substrate, showcasing epitaxial relationship and relaxed TI layer growth.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Multidisciplinary
Fei Wang, Yi-Fan Zhao, Zi-Jie Yan, Deyi Zhuo, Hemian Yi, Wei Yuan, Lingjie Zhou, Weiwei Zhao, Moses H. W. Chan, Cui-Zu Chang
Summary: In this study, we synthesized doped Bi2Te3 thin films with controlled doping concentrations using molecular beam epitaxy. By conducting magneto-transport measurements, we observed an unusual ferromagnetic response in both chromium (Cr)- and vanadium (V)-doped films, where the Curie temperature shows a local maximum at a critical doping concentration. We attribute this behavior to the dopant-concentration-induced magnetic exchange interaction, which transforms the ferromagnetism from van Vleck-type in a nontrivial magnetic topological insulator to Ruderman-Kittel-Kasuya-Yosida (RKKY)-type in a trivial diluted magnetic semiconductor. This work provides insights into the ferromagnetic properties of magnetically doped topological insulator thin films and facilitates the exploration of high-temperature quantum anomalous Hall effect.
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
Physics, Multidisciplinary
Alexander C. Lygo, Binghao Guo, Arman Rashidi, Victor Huang, Pablo Cuadros-Romero, Susanne Stemmer
Summary: By reducing the thickness of thin films of three-dimensional topological insulators, it is possible to create two-dimensional topological insulators. We have observed the first 2D TI state in epitaxial thin films of cadmium arsenide.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Guanzhong Wu, Dongying Wang, Nishchhal Verma, Rahul Rao, Yang Cheng, Side Guo, Guixin Cao, Kenji Watanabe, Takashi Taniguchi, Chun Ning Lau, Fengyuan Yang, Mohit Randeria, Marc Bockrath, P. Chris Hammel
Summary: In this study, we report the emergence of perpendicular magnetic anisotropy and enhanced Gilbert damping induced by interfacial interactions in a heterostructure made of YIG and WTe2. The ability of WTe2 to enhance PMA in FM thin film, combined with its capability to generate out-of-plane damping like spin torque, makes it desirable for magnetic memory applications.
Article
Nanoscience & Nanotechnology
Bin Peng, Haowen Tang, Yuxin Cheng, Yao Zhang, Ruibin Qiu, Qi Lu, Ziyao Zhou, Ming Liu
Summary: This study demonstrates a method to enhance the magnetoelectric coupling effect in multiferroic composite thin films under a strong electric field by utilizing the large dielectric strength of ferroelectric thin films. The voltage control of perpendicular magnetic anisotropy (PMA) in PNZT/(Co/Pt)(5) thin films has been achieved at room temperature. These thin films with large breakdown strength provide a useful platform for enabling integrated multiferroic devices.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Nanoscience & Nanotechnology
Bin Peng, Haowen Tang, Yuxin Cheng, Yao Zhang, Ruibin Qiu, Qi Lu, Ziyao Zhou, Ming Liu
Summary: Multiferroic composite thin films with large breakdown strength provide a useful platform for enabling integrated multiferroic devices. The two-layer PNZT thin films with a thickness of about 200 nm exhibit the highest breakdown strength and small surface roughness, while PNZT/(Co/Pt)5 thin films with strong PMA show voltage-induced effective magnetic field that can induce magnetization switching under strong electric fields.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Physics, Applied
Nguyen Huynh Duy Khang, Takanori Shirokura, Tuo Fan, Mao Takahashi, Naoki Nakatani, Daisuke Kato, Yasuyoshi Miyamoto, Pham Nam Hai
Summary: Topological insulators (TIs) are potential materials for spin-orbit torque (SOT) switching due to their large spin Hall angle. This study investigated SOT magnetization switching in both thermal activation and fast switching regimes using BiSb topological insulator. The results show differences in zero-Kelvin threshold switching current density for the two regimes, and suggest the potential of BiSb thin film for ultra-low power and fast operation of SOT-based spintronic devices.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Takanori Shirokura, Kou Fujiwara, Pham Nam Hai
Summary: The spin Hall effect in amorphous YPt alloy is found to be strongly sensitive to resistivity, governed by both intrinsic and extrinsic mechanisms. Despite being amorphous, the spin relaxation length in YPt is longer than expected for crystallized Pt-based alloys with the same resistivity.
APPLIED PHYSICS EXPRESS
(2021)
Article
Physics, Applied
Nguyen Thanh Tu, Tomohiro Otsuka, Yuto Arakawa, Le Duc Anh, Masaaki Tanaka, Pham Nam Hai
Summary: In this study, the spin-dependent transport properties of fully ferromagnetic p-n junctions were systematically investigated, and the variation of magnetoresistance with the GaSb thickness was found. When the n-type (In,Fe)As layer was used in the structure, a giant magnetoresistance of over 500% was observed.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Multidisciplinary Sciences
Tuo Fan, Nguyen Huynh Duy Khang, Soichiro Nakano, Pham Nam Hai
Summary: In this work, ultrahigh efficient and robust SOT magnetization switching is demonstrated in fully sputtered BiSb topological insulator and perpendicularly magnetized Co/Pt multilayers. Despite being fabricated by magnetron sputtering, the BiSb topological insulator shows a large spin Hall angle and high electrical conductivity, proving its potential for ultralow power SOT-MRAM and other SOT-based spintronic devices.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Applied
Nguyen Huynh Duy Khang, Takanori Shirokura, Tuo Fan, Mao Takahashi, Naoki Nakatani, Daisuke Kato, Yasuyoshi Miyamoto, Pham Nam Hai
Summary: Topological insulators (TIs) are potential materials for spin-orbit torque (SOT) switching due to their large spin Hall angle. This study investigated SOT magnetization switching in both thermal activation and fast switching regimes using BiSb topological insulator. The results show differences in zero-Kelvin threshold switching current density for the two regimes, and suggest the potential of BiSb thin film for ultra-low power and fast operation of SOT-based spintronic devices.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
J. Sasaki, H. H. Huy, N. H. D. Khang, P. N. Hai, Q. Le, B. York, X. Liu, S. Le, C. Hwang, M. Ho, H. Takano
Summary: The role of an interfacial layer in improving the effective spin Hall angle in BiSb (bottom)/FM structures is investigated. It is shown that inserting an optimized thickness interfacial layer helps improve the effective spin Hall angle in the structure.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Multidisciplinary Sciences
Takanori Shirokura, Tuo Fan, Nguyen Huynh Duy Khang, Tsuyoshi Kondo, Pham Nam Hai
Summary: The research team demonstrated the giant spin Hall effect of YPtBi by using half-Heusler alloy topological semi-metal (HHA-TSM), achieving a giant theta(SH) up to 4.1 and a high thermal budget up to 600 degrees C. This material, with high flexibility and compatibility with the BEOL process, opens the door to third-generation spin Hall materials that could be easily adopted by the industry.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Applied
Takanori Shirokura, Tsuyoshi Kondo, Pham Nam Hai
Summary: In this study, we investigated the effect of stoichiometry on the spin Hall angle of YPtBi, a half-Heusler alloy topological semimetal. By changing the composition ratio of Y/Pt, we found that YPtBi with high C1 ordering can be deposited, and it exhibits a large effective spin Hall angle even when the stoichiometry is not exact. This suggests that the spin Hall effect in YPtBi is robust against changes in its stoichiometry.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
M. Kobayashi, N. H. D. Khang, T. Takeda, K. Araki, R. Okano, M. Suzuki, K. Kuroda, K. Yaji, K. Sugawara, S. Souma, K. Nakayama, K. Yamauchi, M. Kitamura, K. Horiba, A. Fujimori, T. Sato, S. Shin, M. Tanaka, P. N. Hai
Summary: In this study, MnGa thin films with the L1(0) structure were investigated using ARPES technique. It was observed that a large Fermi surface with a rhombic shape and an electron pocket formed at the corner of the rhombic Fermi surface. Based on the experimental findings, the relationship between the observed band structure and the spin-dependent properties in MnGa-based heterostructures was discussed.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Multidisciplinary Sciences
Iriya Muneta, Takanori Shirokura, Pham Nam Hai, Kuniyuki Kakushima, Kazuo Tsutsui, Hitoshi Wakabayashi
Summary: Layered materials, like graphene and transition metal dichalcogenides, can exhibit new properties through modification of their crystal arrangements. This study demonstrates the modulation of ferromagnetism in polycrystalline MoS2 using ultralow current density, providing direct evidence of current modulation of ferromagnetism induced by grain boundaries. This finding opens up new possibilities for low power consumption magnetization switching in magnetic random access memories.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Applied
Ho Hoang Huy, Julian Sasaki, Nguyen Huynh Duy Khang, Shota Namba, Pham Nam Hai, Quang Le, Brian York, Cherngye Hwang, Xiaoyong Liu, Michael Gribelyuk, Xiaoyu Xu, Son Le, Michael Ho, Hisashi Takano
Summary: Shrinking the size of a tunneling magnetoresistance (TMR) reader to below 20 nm for magnetic recording technology beyond 4 Tb/in2 is technically challenging due to its complex film stack. We propose a reader architecture based on the inverse spin Hall effect, called spin-orbit torque (SOT) reader, which consists of a SOT layer and a ferromagnetic layer to resolve these challenges. By integrating BiSb topological insulator with strong inverse spin Hall effect into the SOT reader, we improve the output voltage and signal-to-noise ratio (SNR). Our work demonstrates the potential of BiSb for SOT reader beyond 4 Tb/in2 magnetic recording technology.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Julian Sasaki, Shota Namba, Shigeki Takahashi, Yoshiyuki Hirayama, Pham Nam Hai
Summary: BiSb is a topological insulator with both a massive spin Hall effect and high electrical conductivity, which are essential for ultralow power spin-orbit-torque magnetoresistive random access memory. However, when a ferromagnetic (FM) thin film is deposited on top of a BiSb layer, the presence of large surface roughness and Sb diffusion into the FM film significantly reduces the effective spin Hall angle, θSHeff.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Takanori Shirokura, Pham Nam Hai
Summary: The researchers investigated the crystallinity and spin Hall effect of YPtBi thin films grown at lower growth temperature (down to 300 ℃). Although both effective spin Hall angle and spin Hall conductivity degraded with lowering the growth temperature to 300 ℃, they were recovered by reducing the sputtering Ar gas pressure.
Article
Physics, Applied
Takanori Shirokura, Pham Nam Hai
Summary: In this study, we experimentally investigated the spin Hall effect in BiSb topological insulator from room temperature to 125°C. Despite the decreasing effective spin Hall angle with increasing temperature, BiSb maintained a high spin Hall angle of 4.9 even at 125°C, demonstrating its potential for high temperature applications. Furthermore, the temperature-dependence of the spin Hall conductivity indicated that the topological surface states are the origin of the giant spin Hall effect in BiSb.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
H. H. Huy, J. Sasaki, N. H. D. Khang, S. Namba, P. N. Hai, Q. Le, B. York, C. Hwang, X. Liu, M. Gribelyuk, X. Xu, S. Le, R. Nagabhirava, M. Ho, H. Takano
Summary: A spin-orbit torque (SOT) reader using the inverse spin Hall effect was proposed for magnetic recording beyond 4 Tbit/in(2). However, conventional heavy metals have small spin Hall angles, resulting in low output voltage and SNR. This work demonstrated a large spin Hall angle of 2.6-5.1 in sputtered BiSb, a topological insulator, on various ferromagnets with in-plane magnetization, showing promise for SOT readers with high output and SNR.
IEEE TRANSACTIONS ON MAGNETICS
(2023)
Article
Multidisciplinary Sciences
Shobhit Goel, Nguyen Huynh Duy Khang, Yuki Osada, Le Duc Anh, Pham Nam Hai, Masaaki Tanaka
Summary: We demonstrate room-temperature spin injection using spin pumping in a BiSb/(Ga,Fe)Sb heterostructure, where (Ga,Fe)Sb is a ferromagnetic semiconductor with high Curie temperature and BiSb is a topological insulator. Despite the small magnetization of (Ga,Fe)Sb at room temperature, we detected spin injection from (Ga,Fe)Sb by utilizing the large inverse spin Hall effect in BiSb. This study provides the first demonstration of room-temperature spin injection from a ferromagnetic semiconductor.
SCIENTIFIC REPORTS
(2023)
