scholarly journals Field-free spin-orbit torque-induced switching of perpendicular magnetization in a ferrimagnetic layer with a vertical composition gradient

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhenyi Zheng ◽  
Yue Zhang ◽  
Victor Lopez-Dominguez ◽  
Luis Sánchez-Tejerina ◽  
Jiacheng Shi ◽  
...  
Keyword(s):  
Bias Field ◽  
Composition Gradient ◽  
Spin Orbit ◽  
Plane Symmetry ◽  
Micromagnetic Simulations ◽  
Practical Applications ◽  
Spintronic Devices ◽  
Perpendicular Magnetization ◽  
Inversion Asymmetry

AbstractCurrent-induced spin-orbit torques (SOTs) are of interest for fast and energy-efficient manipulation of magnetic order in spintronic devices. To be deterministic, however, switching of perpendicularly magnetized materials by SOT requires a mechanism for in-plane symmetry breaking. Existing methods to do so involve the application of an in-plane bias magnetic field, or incorporation of in-plane structural asymmetry in the device, both of which can be difficult to implement in practical applications. Here, we report bias-field-free SOT switching in a single perpendicular CoTb layer with an engineered vertical composition gradient. The vertical structural inversion asymmetry induces strong intrinsic SOTs and a gradient-driven Dzyaloshinskii–Moriya interaction (g-DMI), which breaks the in-plane symmetry during the switching process. Micromagnetic simulations are in agreement with experimental results, and elucidate the role of g-DMI in the deterministic switching processes. This bias-field-free switching scheme for perpendicular ferrimagnets with g-DMI provides a strategy for efficient and compact SOT device design.

scholarly journals Controllable field-free switching of perpendicular magnetization through bulk spin-orbit torque in symmetry-broken ferromagnetic films

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xuejie Xie ◽  
Xiaonan Zhao ◽  
Yanan Dong ◽  
Xianlin Qu ◽  
Kun Zheng ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Domain Walls ◽  
Single Layer ◽  
Ferromagnetic Film ◽  
Effective Field ◽  
Composition Gradient ◽  
Spin Orbit ◽  
Interlayer Exchange Coupling ◽  
Magnetization Switching ◽  
Perpendicular Magnetization

AbstractProgrammable magnetic field-free manipulation of perpendicular magnetization switching is essential for the development of ultralow-power spintronic devices. However, the magnetization in a centrosymmetric single-layer ferromagnetic film cannot be switched directly by passing an electrical current in itself. Here, we demonstrate a repeatable bulk spin-orbit torque (SOT) switching of the perpendicularly magnetized CoPt alloy single-layer films by introducing a composition gradient in the thickness direction to break the inversion symmetry. Experimental results reveal that the bulk SOT-induced effective field on the domain walls leads to the domain walls motion and magnetization switching. Moreover, magnetic field-free perpendicular magnetization switching caused by SOT and its switching polarity (clockwise or counterclockwise) can be reversibly controlled in the IrMn/Co/Ru/CoPt heterojunctions based on the exchange bias and interlayer exchange coupling. This unique composition gradient approach accompanied with electrically controllable SOT magnetization switching provides a promising strategy to access energy-efficient control of memory and logic devices.

scholarly journals Theoretical Study of Field-Free Switching in PMA-MTJ Using Combined Injection of STT and SOT Currents

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1345
Author(s):  
Shaik Wasef ◽  
Hossein Fariborzi
Keyword(s):  
Critical Current ◽  
Theoretical Study ◽  
Tunnel Junctions ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Orbit ◽  
Micromagnetic Simulations ◽  
Spintronic Devices ◽  
Current Densities ◽  
The Relationship

Field-free switching in perpendicular magnetic tunnel junctions (P-MTJs) can be achieved by combined injection of spin-transfer torque (STT) and spin-orbit torque (SOT) currents. In this paper, we derived the relationship between the STT and SOT critical current densities under combined injection. We included the damping–like torque (DLT) and field-like torque (FLT) components of both the STT and SOT. The results were derived when the ratio of the FLT to the DLT component of the SOT was positive. We observed that the relationship between the critical SOT and STT current densities depended on the damping constant and the magnitude of the FLT component of the STT and the SOT current. We also noted that, unlike the FLT component of SOT, the magnitude and sign of the FLT component of STT did not have a significant effect on the STT and SOT current densities required for switching. The derived results agreed well with micromagnetic simulations. The results of this work can serve as a guideline to model and develop spintronic devices using a combined injection of STT and SOT currents.

scholarly journals Spin-orbit torque manipulated by fine-tuning of oxygen-induced orbital hybridization

2019 ◽  
Vol 5 (11) ◽  
pp. eaax4278 ◽  
Author(s):  
Yuito Kageyama ◽  
Yuya Tazaki ◽  
Hongyu An ◽  
Takashi Harumoto ◽  
Tenghua Gao ◽  
...  
Keyword(s):  
Nonvolatile Memory ◽  
Scale Effects ◽  
Perpendicular Magnetic Anisotropy ◽  
Atomic Scale ◽  
Fine Tuning ◽  
Spin Orbit ◽  
Spintronic Devices ◽  
Fast Switching ◽  
Orbital Hybridization

Current-induced spin-orbit torques provide an effective way to manipulate magnetization in spintronic devices, promising for fast switching applications in nonvolatile memory and logic units. Recent studies have revealed that the spin-orbit torque is strongly altered by the oxidation of heterostructures with broken inversion symmetry. Although this finding opens a new field of metal-oxide spin-orbitronics, the role of the oxidation in the spin-orbit physics is still unclear. Here, we demonstrate a marked enhancement of the spin-orbit torque induced by a fine-tuning of oxygen-induced modification of orbital hybridization. This is evidenced by a concomitant enhancement of the interface spin-orbit torque, interface spin loss, and interface perpendicular magnetic anisotropy within a narrow range of the oxidation level of metallic heterostructures. This result reveals the crucial role of the atomic-scale effects in the generation of the spin-orbit torques, opening the door to atomic-level engineering of the spin-orbit physics.

scholarly journals Time-Resolved Detection of Multilevel Switching of the Magnetization and Exchange Bias Driven by Spin-Orbit Torques

2021 ◽  
Author(s):  
Yuyan Wang ◽  
Takuya Taniguchi ◽  
Po-Hung Lin ◽  
Daniel Zicchino ◽  
Andreas Nickl ◽  
...  
Keyword(s):  
Current Pulse ◽  
Exchange Bias ◽  
High Speed ◽  
Great Promise ◽  
Spin Orbit ◽  
Magnetization Switching ◽  
Time Resolved ◽  
Micromagnetic Simulations ◽  
Spintronic Devices ◽  
Open Questions

Abstract Current induced magnetization switching, jointly with the manipulation of exchange bias, via spin-orbit torques (SOT) on sub-nanosecond timescales hold great promise for fast and low-power spintronic devices. Specifically, the time-resolved detection and subsequent analysis of switching trajectories relevant to ferromagnet/antiferromagnet exchange biased structures are central to designing SOT devices with high speed, and are still open questions. Here, we report the SOT-induced multileveled switching on sub-nanosecond timescales in Pt/Co/IrMn heterostructures, and illustrate the time-resolved magnetization switching trajectories of the exchange bias. By adopting time-resolved magneto-optical Kerr microscopy combined with micromagnetic simulations, our work reveals that not only the ferromagnets, but also the multiple antiferromagnetic domains and exchange bias, can be partially switched by sub-nanosecond current pulse, to flexibly control the switching probabilities at multiple levels. The experiments demonstrate that the SOT switching of exchange bias, which immediately depends on the current density, can significantly stabilize the multileveled magnetization switching within sub-nanosecond current pulse with high thermal stability.

scholarly journals Dzyaloshinskii–Moriya interaction in noncentrosymmetric superlattices

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Woo Seung Ham ◽  
Abdul-Muizz Pradipto ◽  
Kay Yakushiji ◽  
Kwangsu Kim ◽  
Sonny H. Rhim ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Degrees Of Freedom ◽  
Orbit Coupling ◽  
Inversion Symmetry ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Band Formation ◽  
Research Activities ◽  
Moriya Interaction

AbstractDzyaloshinskii–Moriya interaction (DMI) is considered as one of the most important energies for specific chiral textures such as magnetic skyrmions. The keys of generating DMI are the absence of structural inversion symmetry and exchange energy with spin–orbit coupling. Therefore, a vast majority of research activities about DMI are mainly limited to heavy metal/ferromagnet bilayer systems, only focusing on their interfaces. Here, we report an asymmetric band formation in a superlattices (SL) which arises from inversion symmetry breaking in stacking order of atomic layers, implying the role of bulk-like contribution. Such bulk DMI is more than 300% larger than simple sum of interfacial contribution. Moreover, the asymmetric band is largely affected by strong spin–orbit coupling, showing crucial role of a heavy metal even in the non-interfacial origin of DMI. Our work provides more degrees of freedom to design chiral magnets for spintronics applications.

scholarly journals Reducing Dzyaloshinskii-Moriya interaction and field-free spin-orbit torque switching in synthetic antiferromagnets

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ruyi Chen ◽  
Qirui Cui ◽  
Liyang Liao ◽  
Yingmei Zhu ◽  
Ruiqi Zhang ◽  
...  
Keyword(s):  
Domain Wall ◽  
Tunnel Junctions ◽  
Low Power Consumption ◽  
Stray Field ◽  
Magnetic Memory ◽  
Spin Orbit ◽  
Theoretic Analysis ◽  
Spintronic Devices ◽  
Deterministic Switching ◽  
Moriya Interaction

AbstractPerpendicularly magnetized synthetic antiferromagnets (SAF), possessing low net magnetization and high thermal stability as well as easy reading and writing characteristics, have been intensively explored to replace the ferromagnetic free layers of magnetic tunnel junctions as the kernel of spintronic devices. So far, utilizing spin-orbit torque (SOT) to realize deterministic switching of perpendicular SAF have been reported while a large external magnetic field is typically needed to break the symmetry, making it impractical for applications. Here, combining theoretic analysis and experimental results, we report that the effective modulation of Dzyaloshinskii-Moriya interaction by the interfacial crystallinity between ferromagnets and adjacent heavy metals plays an important role in domain wall configurations. By adjusting the domain wall configuration between Bloch type and Néel type, we successfully demonstrate the field-free SOT-induced magnetization switching in [Co/Pd]/Ru/[Co/Pd] SAF devices constructed with a simple wedged structure. Our work provides a practical route for utilization of perpendicularly SAF in SOT devices and paves the way for magnetic memory devices with high density, low stray field, and low power consumption.

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