Article
Chemistry, Multidisciplinary
David Cespedes-Berrocal, Heloise Damas, Sebastien Petit-Watelot, Davide Maccariello, Ping Tang, Aldo Arriola-Cordova, Pierre Vallobra, Yong Xu, Jean-Lois Bello, Elodie Martin, Sylvie Migot, Jaafar Ghanbaja, Shufeng Zhang, Michel Hehn, Stephane Mangin, Christos Panagopoulos, Vincent Cros, Albert Fert, Juan-Carlos Rojas-Sanchez
Summary: Spintronics utilizes spin-orbit coupling to produce spin currents and torques, often using heavy metals with large SOC. A new material architecture is introduced, demonstrating strong current-induced torques on ferrimagnetic layers due to Gd 5d states and interface engineering. This platform offers new opportunities for self-torquing single magnetic layers and generating spin currents.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Physical
Qian Chen, Qingjie Guo, Zhaocong Huang, Bin Fang, Shangkun Li, Weiming Lv, Rongxin Li, Yi Luo, Jun Du, Baoshun Zhang, Ya Zhai, Yaming Fan, Zhongming Zeng
Summary: We present a study on spin-orbit torques (SOTs) generated by ferrimagnetic FeCoTb alloys in spin valve structures. Our results show high-efficient damping-like and field-like torques and a spin Hall conductivity of FeCoTb that surpasses that of conventional heavy metals. The magnetization dependent behavior of the SOTs, possibly originating from the anomalous Hall effect dominated by Tb magnetization, can be controlled by manipulating the magnetic configuration. This study highlights the potential of ferrimagnetic materials for low-power spintronic applications.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Review
Chemistry, Multidisciplinary
Giacomo Sala, Pietro Gambardella
Summary: Ferrimagnets, especially rare-earth transition-metal (RE-TM) alloys, exhibit the fastest current-induced dynamics among magnetic materials. Current-induced spin-orbit torques (SOTs) can efficiently switch their magnetization and facilitate fast domain-wall motion. Recent research has shown that the switching process is influenced by significant stochastic fluctuations, but strong SOTs can achieve fast and deterministic sub-nanosecond switching with minimal energy dissipation. Asynchronous responses of the RE and TM magnetizations to SOTs challenge the assumption of rigid inter-sublattice antiferromagnetic coupling. The ability to tailor the timescale and reversal mode of RE-TM alloys offers potential for optimizing the speed of ferrimagnetic spintronic devices and gaining insights into current-induced transfer of angular momentum in systems with ferromagnetic and antiferromagnetic interactions.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Physics, Applied
Junshuai Wang, Chaozhong Li, Rujun Tang, Guozhi Chai, Jinli Yao, Changjun Jiang
Summary: We report spin-orbit torque based on spin-torque ferromagnetic resonance in a single ferrimagnetic layer. By investigating temperature-dependent anomalous Hall resistance and ST FMR, we quantify the spin-orbit torque and observe its sign divergence as the temperature approaches the magnetic compensation temperature.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Lin Liu, Ziqi Fan, Zhiren Chen, Zehan Chen, Zhixiang Ye, Hongnan Zheng, Qi Zeng, Wei Jia, Shuoqi Li, Ning Wang, Jing Liu, Lei Ma, Tao Lin, Mingxia Qiu, Shunpu Li, Peigang Han, Ji Shi, Hongyu An
Summary: This study reports the investigation of SOT in FMI near compensation tuned by temperature. The experiment shows that SOT generation is significantly enhanced near the compensation temperature due to the decrease in net magnetization. The effective spin Hall angle in Pt/GdIG bilayer films is estimated to be around 0.0073, with little dependence on temperature.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Yassine Quessab, Jun-Wen Xu, Md Golam Morshed, Avik W. Ghosh, Andrew D. Kent
Summary: Ferrimagnetic thin films are preferred for low-power spintronic applications due to their low magnetization, small angular momentum, and fast spin dynamics. Pt/CoGd/(W or Ta) films enable more energy-efficient SOT magnetization switching compared to Pt/CoGd/Ir, with Pt/CoGd/W having the highest spin-Hall angle and efficiency.
Article
Materials Science, Multidisciplinary
Heloise Damas, Alberto Anadon, David Cespedes-Berrocal, Junior Alegre-Saenz, Jean-Lois Bello, Aldo Arriola-Cordova, Sylvie Migot, Jaafar Ghanbaja, Olivier Copie, Michel Hehn, Vincent Cros, Sebastien Petit-Watelot, Juan-Carlos Rojas-Sanchez
Summary: Spintronics has made promising progress in finding new materials and effects to reduce energy consumption in information technology. This study investigates the generation of spin currents in a GdFeCo/Cu/NiFe trilayer system, where the FeCo sublattice magnetization dominates at room temperature. The researchers successfully obtained the effective fields and spin Hall angles through spin-torque ferromagnetic resonance measurements with an added dc current. The study provides insights for tuning spin conversion in highly efficient ferrimagnetic systems.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Lijun Zhu, Daniel C. Ralph, Robert A. Buhrman
Summary: The study investigates the mechanism of unexpected bulk spin-orbit torques (SOTs) in magnetic single-layers by utilizing chemically disordered FexPt1-x. It is found that the bulk dampinglike SOT arises from an imbalanced internal spin current and is sensitive to the presence of a vertical composition gradient. The discovery suggests the potential development of low-power single-layer SOT devices through strain engineering.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Physics, Applied
Shunsuke Yanai, Daiki Oshima, Shigeki Takahashi, Yoshiyuki Hirayama, Takeshi Kato
Summary: The thickness dependence of spin-orbit torque (SOT) and critical current density of SOT switching in Gd/FeCo multilayers were studied and compared with GdFeCo alloy/Ta bilayers. The critical current density of SOT switching in the multilayers was similar to the alloy films. The damping-like and field-like SOT effective fields increased near the compensation point in the multilayers, and the change in sign of the field-like SOT was also observed, similar to the alloy.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Akanksha Chouhan, Heston A. Mendonca, Sutapa Dutta, Ambika Shanker Shukla, Rachit R. Pandey, Ashwin A. Tulapurkar
Summary: This study investigates the evolution of spin-orbit torque efficiencies under mechanical strain and reports an enhancement in damping-like and field-like spin-orbit torque efficiencies due to tensile strain.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Martin Testa-Anta, Charles-Henri Lambert, Can Onur Avci
Summary: Spin-orbit torques (SOTs) in heavy metal (HM)/magnetic insulator (MI) bilayers attract increasing attention due to their tunable magnetic properties and insulating nature. However, accurate determination of SOTs in MIs is limited by low electrical signals and dominant spurious thermoelectric effects. A simple method based on harmonic Hall voltage detection and macrospin simulations is reported, accurately quantifying the damping-like and field-like SOTs, and thermoelectric contributions separately in MI-based systems. This method yields precise values for SOTs in the Bi-doped YIG/Pt heterostructure and reveals the influence of current-induced Joule heating on spin transparency and SOTs.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Xin Lin, Jingwei Li, Lujun Zhu, Xinyue Xie, Qianbiao Liu, Dahai Wei, Guodong Yuan, Lijun Zhu
Summary: We report a strong enhancement of spin-orbit torques in dirty metal Pt by incorporating Si3N4 impurities. The enhancement is attributed to the optimized trade-off between the intrinsic spin Hall conductivity and the spin carrier lifetime in the dirty limit, resulting in a twofold increase in the dampinglike spin-orbit torque per unit current density in Pt-x(Si3N4)(1-x)/Co0.65Tb0.35 bilayers. We also find that only 58% of the angular momentum of the spin current contributes to spin torque generation.
Article
Nanoscience & Nanotechnology
Tianli Jin, Gerard Joseph Lim, Han Yin Poh, Shuo Wu, Funan Tan, Wen Siang Lew
Summary: This study proposes a technique to modulate the spin reflection and spin density of states within a heavy-metal Pt through interfacing with a dielectric MgO layer. The researchers demonstrate tunability of the effective out-of-plane spin torque acting on the ferromagnetic Co layer, enabling current-induced SOT magnetization switching without the assistance of an external magnetic field. The influence of the MgO layer thickness on effective SOT efficiency shows saturation at 4 nm, while up to 80% of field-free magnetization switching ratio is achieved with the MgO between 5 and 8 nm. By substituting the dielectric with Ti or Pt, the researchers confirm that the MgO layer is indeed responsible for the observed field-free magnetization switching mechanism.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Nanoscience & Nanotechnology
Yong-Chang Lau, Takeshi Seki, Koki Takanashi
Summary: This study presents a systematic comparative analysis of spin Hall efficiency in highly face-centered cubic (fcc) Pt-Al alloy films and poorly crystallized Pt-Al alloy films. The results indicate that fcc Pt100-xAlx alloy films grown on MgO exhibit outstanding charge-spin conversion efficiency, showing the potential for reducing power consumption compared to polycrystalline bilayers on SiO2. Improving the crystallinity of fcc Pt-based alloys is shown to be crucial for achieving large spin Hall efficiency and low power consumption.
Article
Materials Science, Multidisciplinary
T. Z. Zhang, K. K. Meng, Y. Wu, J. K. Chen, S. G. Wang, X. G. Xu, Y. Jiang
Summary: We investigated the spin-orbit torques (SOTs) driven interfacial magnetization switching in α-Fe2O3/Pt bilayers through various transport measurements. The interfacial magnetic state is a result of the strong spin-orbit coupling in the Pt layer and the magnetic-field-dependent bulk magnetic order in the α-Fe2O3 layer. The dominant role of the fieldlike SOT and its nonlinear relationship with the current amplitude and magnetic field suggests the involvement of interfacial magnetic order. The research on magnetic textures in antiferromagnetic insulator/heavy metal bilayers provides an exciting platform for studying spin transport.
Article
Chemistry, Multidisciplinary
Jimin Jeong, Min-Gu Kang, Soogil Lee, Jaimin Kang, Kyung-Jin Lee, Byong-Guk Park
Summary: In this study, the modulation of magnetic easy-cone states through voltage-controlled magnetic anisotropy (VCMA) significantly reduced the SOT switching current. The SOT switching current density is reduced by up to 50% when the easy-cone angle is changed from 0 degrees to 58 degrees. The magnetic easy-cone state is gradually modulated in a reversible and non-volatile manner, facilitating multilevel spintronic devices.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Physics, Applied
Ik-Sun Hong, Se Kwon Kim, Kyung-Jin Lee, Gyungchoon Go
Summary: A magnonic version of the Fabry-Perot interferometer is proposed, utilizing the interaction between magnetic domain walls and spin waves. By adjusting the distance between two domain walls, the magnon wavelength passing through the interferometer can be tuned, offering a way to enhance magnonic information processing capability in a simple magnetic structure.
APPLIED PHYSICS LETTERS
(2021)
Review
Chemistry, Physical
Se Kwon Kim, Geoffrey S. D. Beach, Kyung-Jin Lee, Teruo Ono, Theo Rasing, Hyunsoo Yang
Summary: Ferrimagnets, composed of multiple antiferromagnetically coupled magnetic elements, offer advantages of both ferromagnets and antiferromagnets, including easy control of magnetization by external field, faster dynamics than ferromagnets, and potential for high-density devices. This Review provides a summary of recent progress in ferrimagnetic spintronics, focusing on functionalities such as spin transport, spin texture dynamics, and all-optical switching.
Article
Physics, Applied
Yune-Seok Nam, Dae-Yun Kim, Yong-Keun Park, Ji-Sung Yu, Seong-Hyub Lee, Duck-Ho Kim, Byoung-Chul Min, Sug-Bong Choe
Summary: Here, researchers propose an experimental scheme to determine the strength of the Heisenberg exchange interaction in ultrathin magnetic films. The scheme analyzes the chirality transition between different types of domain walls under an in-plane magnetic field and estimates the exchange stiffness constant based on this analysis. The scheme, which utilizes the magneto-optical Kerr effect, is applicable to ultrathin magnetic films down to a few atomic layers.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Deok Hyun Yun, TaeHyuk Kwon, Ki-Hyuk Han, Dong Joon Lee, Seokmin Hong, Hyun Cheol Koo, Byoung-Chul Min, Byeong-Kwon Ju, OukJae Lee
Summary: In this study, the magnetic properties of Pt/CoFeB/MgO layers were investigated using the angle-resolved spin-torque ferromagnetic resonance method. The measurements provided reasonable magnetic parameters, but an unusual value was obtained for the interfacial spin transparency. The thickness dependence of the Lande g-factor for CoFeB indicated that the interfacial spin-orbit coupling played a role in determining the enhancement of magnetic damping. Furthermore, the azimuthal asymmetry in the magnetic system may not be related to unconventional spin polarization. These results contribute to the understanding of various magnetic properties and current-induced spin-torques in heavy-metal/ferromagnet bilayers.
JOURNAL OF APPLIED PHYSICS
(2022)
Editorial Material
Multidisciplinary Sciences
Kab-Jin Kim, Kyung-Jin Lee
Summary: Applying strain to an antiferromagnetic material allows its magnetization to be fully switched with an electric current, making it significant for next-generation magnetic memory devices.
Article
Physics, Multidisciplinary
Hyeon-Jong Park, Hye-Won Ko, Gyungchoon Go, Jung Hyun Oh, Kyoung-Whan Kim, Kyung-Jin Lee
Summary: In this study, we theoretically demonstrate the spin swapping effect in centrosymmetric ferromagnets, which is mediated by an orbital degree of freedom and does not require inversion asymmetry or impurity spin-orbit scattering. Our research emphasizes the important role of the orbital degree of freedom in describing spin-orbit-coupled transport in centrosymmetric materials.
PHYSICAL REVIEW LETTERS
(2022)
Article
Multidisciplinary Sciences
Jong-Guk Choi, Jaehyeon Park, Min-Gu Kang, Doyoon Kim, Jae-Sung Rieh, Kyung-Jin Lee, Kab-Jin Kim, Byong-Guk Park
Summary: This study shows that the frequency of SHNOs can be controlled up to 2.1 GHz by an electric field, enabling large frequency tuning. The voltage-controlled frequency tuning of SHNOs facilitates the development of energy-efficient neuromorphic devices. Additionally, repetitive voltage pulses can be used to cumulatively control the frequency, mimicking the functions of biological synapses.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Applied
Ji-Sung Yu, Dae-Yun Kim, Joon Moon, Seong-Hyub Lee, Jun-Young Chang, Duck-Ho Kim, Byoung-Chul Min, Sug-Bong Choe
Summary: Dzyaloshinskii-Moriya interaction (DMI) plays a crucial role in the formation and stability of chiral magnetic objects and also determines their roughness. Experimental observations on magnetic multilayer films reveal the relationship between DMI and the roughness of chiral domain-walls. This study provides a quantitative method to determine the DMI-induced effective field, which is an important parameter for the stability and dynamic characteristics of chiral domain-walls.
APPLIED PHYSICS LETTERS
(2022)
Article
Computer Science, Hardware & Architecture
Taehwan Kim, Yunho Jang, Min-Gu Kang, Byong-Guk Park, Kyung-Jin Lee, Jongsun Park
Summary: This paper proposes a spin-orbit torque magnetic random access memory (SOT-MRAM) based digital PIM architecture, utilizing SLIM cells and CRISP architecture to alleviate the burden of additional memory size and computation cycle issues, while considering a pipelining scheme to increase throughput.
IEEE TRANSACTIONS ON COMPUTERS
(2022)
Article
Multidisciplinary Sciences
Kyuhwe Kang, Hiroki Omura, Daniel Yesudas, OukJae Lee, Kyung-Jin Lee, Hyun-Woo Lee, Tomoyasu Taniyama, Gyung-Min Choi
Summary: In this study, the spin current in a FeRh/Cu heterostructure during the ultrafast magnetization process is directly measured, revealing a significant correlation between the spin current and the magnetization dynamics. This suggests an angular momentum transfer mechanism from electrons to magnons, involving spatial transport and dissipation of angular momentum. This finding contributes to a better understanding of laser-induced ultrafast magnetization processes.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Eun-Sang Park, Dong-Kyu Lee, Fei Xue, Byoung-Chul Min, Hyun Cheol Koo, Paul M. Haney, Kyoung-Whan Kim, Kyung-Jin Lee
Summary: The symmetry of normal metal/ferromagnet bilayers allows spin-orbit torques (SOTs) to have two distinct angular dependences on the magnetization direction. The most studied forms of SOT are the lowest-order SOT, which consist of fieldlike and dampinglike torques. There are also higher-order SOT forms that have different spin polarization and an additional factor of magnetization direction dependence. This study measures both the lowest-order and higher-order angular dependences of SOTs in three types of bilayers and finds that the higher-order SOT is dominant for one type of bilayer while negligible for the others. Macrospin simulations show that higher-order SOT can significantly affect magnetization dynamics, which aligns with SOT-induced switching experiments.
Article
Materials Science, Multidisciplinary
Jaechul Shim, Kyung-Jin Lee
Summary: Highly entangled states are crucial for quantum information processing. In this study, we theoretically investigate magnon-magnon entanglement in a compensated ferrimagnet and find that the steady-state magnon-magnon entanglement is significantly enhanced near the angular momentum compensation point when magnons are coupled with photons in a cavity. This enhancement is attributed to the ability of the ground state of the ferrimagnet to approach the Einstein-Podolsky-Rosen state. This unique feature of ferrimagnets with different Lande g factors between sublattices results in higher magnon entanglement compared to ferromagnets and antiferromagnets.
Article
Materials Science, Multidisciplinary
Eun-Sang Park, DongJoon Lee, OukJae Lee, Byoung-Chul Min, Hyun Cheol Koo, Kyoung-Whan Kim, Kyung-Jin Lee
Summary: This theoretical investigation focused on spin-orbit torques in insulator/ferromagnet/normal-metal structures, particularly on the interfacial spin-orbit coupling effect at an insulator/ferromagnet interface. The study found that the interfacial spin-orbit coupling contributes to dampinglike spin-orbit torque, crucial for current-driven magnetization dynamics, even when it generates only the fieldlike component. Additionally, spin-orbit torques in a single ferromagnet between two dissimilar insulators were calculated, providing further insights into interfacial spin-orbit interaction at insulator/ferromagnet interfaces.
Article
Materials Science, Multidisciplinary
Dong-Hyun Kim, Se-Hyeok Oh, Dong-Kyu Lee, Se Kwon Kim, Kyung-Jin Lee
Summary: The study investigates the modification of ferrimagnetic spin-wave dynamics induced by electrical current, showing that the sign of the Doppler shift is influenced by the handedness of spin waves. When electrons move in the same direction as spin-wave propagation, the attenuation lengths of both right- and left-handed spin waves increase.
