Article
Physics, Applied
Haihong Yin, Xiangyu Zheng, Junlin Wang, Yu Zhou, Balati Kuerbanjiang, Guanqi Li, Xianyang Lu, Kaiyu Tong, Yichuan Wang, Jing Wu, Vlado K. Lazarov, Richard F. L. Evans, Roy W. Chantrell, Jianwang Cai, Bo Liu, Hao Meng, Yongbing Xu
Summary: The study reveals that Skyrmions are more likely to form in samples with higher amounts of structural defects, and the density of Skyrmions can be controlled by artificial tuning of the defect amount. By utilizing first-order reversal curves, the stable region and density of Skyrmions can be efficiently controlled in return magnetization loops.
APPLIED PHYSICS LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Soubhik Kayal, Saikat Maji, Ankan Mukhopadhyay, P. S. Anil Kumar
Summary: In this study, we investigated a heterostructure with perpendicular magnetic anisotropy and broken lateral symmetry. By utilizing the spin-Hall effect and lateral space inversion asymmetry, we enhanced the efficiency of spin-orbit torque and achieved a lower critical current density for current-induced magnetization reversal.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Lizhu Ren, Chenghang Zhou, Xiaohe Song, Herng Tun Seng, Liang Liu, Chaojiang Li, Tieyang Zhao, Zhenyi Zheng, Jun Ding, Yuan Ping Feng, Jingsheng Chen, Kie Leong Teo
Summary: Electrically manipulating magnetic moments by spin-orbit torque (SOT) has potential applications in magnetic memories and logic devices. In this study, highly textured, polycrystalline Heusler alloy MnxPtyGe (MPG) films were found to exhibit reversible switching of magnetization with low switching current density. Additionally, MPG shows a memristive characteristic and the ability for deterministic field-free switching of magnetization.
Article
Materials Science, Multidisciplinary
Qixun Guo, Zhongxu Ren, He Bai, Xuemin Wang, Guanghua Yu, Wei He, Jiao Teng, Tao Zhu
Summary: The study experimentally investigated the perpendicular magnetic anisotropy properties of CoFeB/MgO films on 3d light-metal vanadium. It observed a sign change of effective torque fields with the increase of vanadium thickness, indicating a competition of multiple effects on current-induced torques in the weakly spin-orbit coupled V/CoFeB/MgO multilayers. These findings have implications for the fundamental understanding of current-induced torque and further device applications using 3d light transition-metal based heterostructures.
Article
Physics, Applied
B. Ravi Kumar, Sreekar Guddeti, P. S. Anil Kumar
Summary: The magnetic field driven domain-wall motion in out-of-plane magnetized Ta/Pt/CoFeB/Pt multilayers, both as-deposited and annealed, was investigated using Kerr microscopy. The study focused on the modified interfacial Dzyaloshinskii-Moriya interaction (iDMI) that controls the dynamics of chiral domain walls. The strength of iDMI was found to decrease with increasing CoFeB thickness and annealing temperature, which can be attributed to changes in the interface properties and annealing-induced effects.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Physics, Multidisciplinary
Houyi Cheng, Boyu Zhang, Yong Xu, Shiyang Lu, Yuxuan Yao, Rui Xiao, Kaihua Cao, Yongshan Liu, Zilu Wang, Renyou Xu, Danrong Xiong, Yan Wang, Helin Ma, Sylvain Eimer, Chao Zhao, Weisheng Zhao
Summary: The study presents a Mo-based perpendicular double free layer structure with a low Gilbert damping constant in magnetic tunnel junctions, which contributes to faster switching speeds and lower power consumption in magnetic random-access memory.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2022)
Article
Chemistry, Multidisciplinary
Surya Narayan Panda, Sudip Majumder, Samiran Choudhury, Arpan Bhattacharya, Sumona Sinha, Anjan Barman
Summary: This study investigates the magnetization dynamics in graphene/ferromagnet hybrid heterostructures and reveals an inverse relationship between ultrafast demagnetization time and Gilbert damping parameter, induced by interfacial spin accumulation and pure spin-current transport. The findings can contribute to the understanding of magnetic damping and aid in the design of graphene-based ultrahigh-speed spintronic devices.
Article
Physics, Applied
Zhuoyi Li, Xianyang Lu, Zhe Zhang, Wenjia Li, TaoTao Li, Jian Zhou, Yu Yan, Ruobai Liu, Jun Du, Ronghua Liu, Xinran Wang, Yao Li, Liang He, Jing Wu, Rong Zhang, Yongbing Xu
Summary: This study conducted a comprehensive investigation on improving the spin-orbit torque (SOT) efficiency of the Ta/CoFeB structure by inserting an oxide insulating layer Fe2O3. It was found that a thickness of only 1-5 nm of Fe2O3 significantly reduced the SOT critical switching current by 70% and enhanced the spin Hall angle of Ta. Both types of spin-orbit torques, damping-like and field-like torques, were significantly enhanced. The observed enhanced SOT efficiency was attributed to the atomic diffusion of O from the Fe2O3 underlayer, leading to the partial oxidization of the Ta layer and the Ta/CoFeB interfaces. The results provide a reliable method to improve the SOT performance in perpendicularly magnetized structures for potential real-world applications in spintronic devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Tetsunori Koda, Sho Muroga, Yasushi Endo
Summary: The magnetization dynamics in La-doped yttrium iron garnet thin film induced by a slot line waveguide with a perpendicular magnetic field is studied. The dimensions of the slot line waveguide significantly affect the magnetization dynamics, particularly increasing the number of excitation conditions with the enlargement of linewidth and the gap between the lines. However, this increase is not observed when the magnetic field is applied in-plane. The excitation is caused by the interaction between the local magnetization dynamics around the line and the spin waves from the other side of the line. When the magnetic field is applied perpendicular to the film, forward volume magnetostatic spin waves are emitted, and their wavelength change shows a gradual dependence on the magnetic field.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Materials Science, Multidisciplinary
Christian Lacroix, Kaan Oguz, John Michael David Coey, David Menard
Summary: The substitution of iron atoms by chromium in CoFeB films has been proposed to reduce the critical current density J(c) for current-driven magnetization switching in spin transfer torque devices by reducing its magnetization. The effect of Cr on the magnetic damping has been investigated through ferromagnetic resonance (FMR) measurements. It was found that introducing Cr increases the spin-orbit damping while reducing the magnetic relaxation rate. Additionally, the presence of Cr inhibits internal fluctuations of the magnetization, reducing the two-magnon damping.
Article
Materials Science, Multidisciplinary
Christian Lacroix, Kaan Oguz, John Michael David Coey, David Menard
Summary: The substitution of iron atoms by chromium in CoFeB films has been proposed to reduce the critical current density J(c) for current-driven magnetization switching in spin transfer torque devices by reducing its magnetization. The effect of Cr on the magnetic damping has remained elusive. Ferromagnetic resonance (FMR) measurements were used to study the different mechanisms of FMR damping in Co40Fe40-xCrxB20 thin films. The results showed that the addition of Cr increases the spin-orbit damping but reduces the magnetic relaxation rate.
Article
Materials Science, Multidisciplinary
A. Harres, T. A. Mallmann, M. Gamino, M. A. Correa, A. D. C. Viegas, R. B. da Silva
Summary: This study experimentally investigates the magnetization reversal processes in amorphous CoFeB thin films of different thicknesses. It concludes that domain wall displacement is the dominant reversal mechanism for films with 200 nm and 300 nm, while coherent rotation becomes important near the hard axis for the thinnest sample even when the external magnetic field is applied away from it.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Weiwei Zhang, Zhanghua Chen, Vladimir I. Belotelov, Yujun Song
Summary: The Kerr null points of ferromagnetic thin films can be controlled by adjusting the thickness of different material layers. The introduction of non-ferromagnetic materials can enhance the Kerr effect of the ferromagnetic thin films.
Article
Physics, Applied
Sang Sun Lee, Tae-Seong Ju, Hee-Sung Han, Mi-Young Im, Changsoo Kim, Kyoung-Woong Moon, Seungmo Yang
Summary: In this study, we investigated the effect of atomic-scale interface engineering by inserting a Ta layer between the CoFeB/MgO interface on perpendicular magnetic anisotropy, saturation magnetization, and Dzyaloshinskii-Moriya interaction. Our findings contribute to the development of optimized CoFeB-based skyrmion hosting materials.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
V. Vlaminck, L. Temdie, V. Castel, M. B. Jungfleisch, D. Stoeffler, Y. Henry, M. Bailleul
Summary: We propose a near-field diffraction model for spin waves in perpendicularly magnetized films, which is applicable in any geometries of excitation fields. This model utilizes the Kalinikos-Slavin formalism to express the dynamic susceptibility tensor in k-space and calculates the diffraction patterns via inverse 2D-Fourier transform of the response functions. We demonstrate a high level of quantitative agreement between our model and MuMax3 micro-magnetic simulations on two different antenna geometries. Our method is of great significance for studying spin wave diffraction in perpendicularly magnetized films and can be readily applied in the future designs of magnon beamforming and interferometric devices.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Finn-Frederik Stiewe, Tristan Winkel, Yuta Sasaki, Tobias Tubandt, Tobias Kleinke, Christian Denker, Ulrike Martens, Nina Meyer, Tahereh Sadat Parvini, Shigemi Mizukami, Jakob Walowski, Markus Muenzenberg
Summary: We investigate the generation of local THz fields using spintronic THz emitters to improve the resolution for micrometer-sized imaging. By employing optical laser pulses as a pump, the THz field generation can be localized to the area of laser beam focusing. Through the use of scanning techniques and gold test patterns, we achieve sub-micrometer spatial resolution at the dimensions of the laser spot size.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Satoshi Iihama, Kazuaki Ishibashi, Shigemi Mizukami
Summary: A recent study reports the control of thin-film magnetization using optical helicity. It was found that stochastic thermal processes, such as magnetic circular dichroism, mediate helicity-dependent magnetization switching, while the photon spin angular momentum plays a secondary role. However, the inverse Faraday effect in ferromagnetic thin films and photon spin angular momentum injection into heavy metal thin films can induce torque on metallic thin-film magnets. This study explores the photon spin angular momentum driven magnetization dynamics in metallic thin-film heterostructures and provides insights for efficient photon-driven magnetization manipulation.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Ruma Mandal, Ivan Kurniawan, Ippei Suzuki, Zhenchao Wen, Yoshio Miura, Takahide Kubota, Koki Takanashi, Tadakatsu Ohkubo, Kazuhiro Hono, Yukiko K. Takahashi
Summary: In this study, a high-quality half-metallic epitaxial nano-scale thick NiMnSb alloy film grown on a Cr/Ag-buffered MgO (001) single crystalline substrate was reported. The highly ordered C1(b) structured nano-scale thick NiMnSb film deposited at 573 K exhibited ultralow Gilbert damping, high anisotropic field, and saturation magnetization. The analysis of theoretical and experimental data revealed a strong correlation between crystal ordering and magnetic parameters, as well as sample quality. The negative anisotropic magnetoresistance ratio demonstrated the robust bulk half-metallicity. This unique combination of highly ordered nano-scale half-metallic NiMnSb alloy with ultralow damping can be advantageous for spintronic device applications.
ACS APPLIED NANO MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
S. Heidtfeld, R. Adam, T. Kubota, K. Takanashi, D. Cao, C. Schmitz-Antoniak, E. Buergler, F. Wang, C. Greb, G. Chen, I. Komissarov, H. Hardtdegen, M. Mikulics, R. Sobolewski, S. Suga, C. M. Schneider
Summary: We successfully generated pulses of electromagnetic radiation with a frequency content up to three terahertz using optical excitation of alloy/heavy metal bilayers. Our findings reveal that the spin diffusion length plays a crucial role in the efficiency of THz radiation.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Kazuma Kunimatsu, Tufan Roy, Jun Okabayashi, Tomoki Tsuchiya, Tomohiro Ichinose, Masahito Tsujikawa, Masafumi Shirai, Shigemi Mizukami
Summary: This study investigates the structure and magnetism of epitaxial thin films, finding that the bcc phase in Co1-xMnx alloys exhibits attractive properties for magnetics and spintronics.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Yuta Sasaki, Ryoya Hiramatsu, Yohei Kota, Takahide Kubota, Yoshiaki Sonobe, Akimasa Sakuma, Koki Takanashi, Shinya Kasai, Yukiko K. Takahashi
Summary: This study investigates the sub-terahertz magnetization precessional motion in Cu2Sb-type MnAlGe and (Mn-Cr)AlGe films using an all-optical pump-probe method. The materials exhibit large perpendicular magnetic anisotropy in nanoscale regions and TEM images confirm the pseudo-2D crystal structures. Cr substitution in (Mn-Cr)AlGe decreases the intrinsic magnetic damping constant, resulting in a magnetization precession frequency of 0.164 THz and small effective magnetic damping constant of 0.012.
Article
Physics, Multidisciplinary
Atsufumi Hirohata, Kelvin Elphick, David C. Lloyd, Shigemi Mizukami
Summary: By categorizing magnetic tunnel junctions into four groups and studying their interfacial atomic structures and spin-polarized electron transport, it is concluded that spin fluctuation induced by dislocations and disordering at a ferromagnet/barrier interface reduces magnetoresistance.
FRONTIERS IN PHYSICS
(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
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
Nanoscience & Nanotechnology
Kazuya Z. Z. Suzuki, Shigemi Mizukami
Summary: We investigated MgO barrier magnetic tunnel junctions (MTJs) comprising perpendicularly magnetized MnGa and FeCoB electrodes. By utilizing thin metastable bcc CoMn alloys as an interlayer between MnGa and MgO, we enhanced the tunnel magnetoresistance (TMR) effect in these perpendicular (p-) MTJs. Additionally, we studied the effect of a thin Mg interlayer between MnGa and CoMn. Through interlayer engineering, we achieved a TMR ratio over 100%, the highest value observed for p-MTJs with a tetragonal MnGa electrode. Our study contributes to the further development of spintronic devices using p-MTJs with various Mn-based tetragonal alloy electrodes.
Article
Physics, Applied
Soki Kobayashi, Hiroki Koizumi, Hideto Yanagihara, Jun Okabayashi, Takahiro Kondo, Takahide Kubota, Koki Takanashi, Yoshiaki Sonobe
Summary: The study investigates the magnetic anisotropy and magnetic interactions at the interface between Fe and NiO(001). The preferential magnetization direction of the ultrathin Fe layer on NiO(001) changed depending on the growth conditions and post-annealing temperature. The lattice constant of NiO(001) layers parallel to the growth direction increased with O2 flow rate, while those parallel to the in-plane direction were locked onto the MgO(001) substrate. Perpendicular magnetization was observed only when the NiO layer was grown with high O2 flow rates. The magnetic anisotropy energies at the interface were temperature-independent, while the coercivity exhibited a significant temperature dependence. The exchange interaction between the ferromagnetic and antiferromagnetic layers was not negligible, despite NiO(001) being a spin-compensated surface.
PHYSICAL REVIEW APPLIED
(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
Chemistry, Physical
Tomohiro Ichinose, Junichi Ikeda, Yuta Onodera, Tomoki Tsuchiya, Kazuya Z. Suzuki, Shigemi Mizukami
Summary: A magnetic tunnel junction (MTJ) is a key device in spintronics applications, such as magnetoresistive random access memory (MRAM). The current standard magnetic material for MTJs is a body-centered cubic (bcc) FeCo(B), which shows large tunnel magnetoresistance (TMR) and high perpendicular magnetic anisotropy (PMA), both crucial for high-memory capacity MRAM. However, bcc Co is thermodynamically unstable, so it is aimed to explore metastable bcc Co based alloys. In this study, we propose a metastable bcc Co based alloy with added Mn and Fe, and demonstrate large TMR effects at both elevated and low temperatures using in-plane magnetized MTJs.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Kazuaki Ishibashi, Satoshi Iihama, Shigemi Mizukami
Summary: A recent study reported a helicity-dependent photocurrent in Bi single-layer thin films. This photocurrent is believed to originate from the combination of photon-spin conversion and spin-charge conversion effects in Bi, with a high efficiency of spin conversion expected in Bi. In this study, two types of terahertz (THz) emissions from Bi/Co bilayer films were measured to investigate spin current induced by laser induced demagnetization of the Co layer and photon-spin conversion effect in the Bi layer simultaneously. The observed different thickness dependences of peak intensity and bandwidth for THz spin current in the two experiments are attributed to the distinct spin relaxation properties of optically excited spin currents in Bi layers.
