More Like this

1. Spin-orbit torque switching of chiral magnetization across a synthetic antiferromagnet

   https://doi.org/10.1038/s42005-020-00513-z  

   Wang, Kang ; Qian, Lijuan ; Ying, See-Chen ; Xiao, Gang ( January 2021 , Communications Physics)

   The interfacial Dzyaloshinskii-Moriya interaction (DMI) holds promises for design and control of chiral spin textures in low-dimensional magnets with efficient current-driven dynamics. Recently, an interlayer DMI has been found to exist across magnetic multilayers with a heavy-metal spacer between magnetic layers. This opens the possibility of chirality in these three-dimensional magnetic structures. Here we show the existence of the interlayer DMI in a synthetic antiferromagnetic multilayer with both inversion and in-plane asymmetry. We analyse the interlayer DMI’s effects on the magnetization and the current-induced spin-orbit torque (SOT) switching of magnetization through a combination of experimental and numerical studies. Themore »chiral nature of the interlayer DMI leads to an asymmetric SOT switching of magnetization under an in-plane magnetic field. Our work paves the way for further explorations on controlling chiral magnetizations across magnetic multilayers through SOTs, which can provide a new path in the design of SOT devices.

   « less
2. Field-free spin-orbit torque-induced switching of perpendicular magnetization in a ferrimagnetic layer with a vertical composition gradient

   https://doi.org/10.1038/s41467-021-24854-7  

   Zheng, Zhenyi ; Zhang, Yue ; Lopez-Dominguez, Victor ; Sánchez-Tejerina, Luis ; Shi, Jiacheng ; Feng, Xueqiang ; Chen, Lei ; Wang, Zilu ; Zhang, Zhizhong ; Zhang, Kun ; et al ( July 2021 , Nature Communications)

   Current-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 amore »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.

   « less
3. Controlling spin current polarization through non-collinear antiferromagnetism

   https://doi.org/10.1038/s41467-020-17999-4  

   Nan, T. ; Quintela, C. X. ; Irwin, J. ; Gurung, G. ; Shao, D. F. ; Gibbons, J. ; Campbell, N. ; Song, K. ; Choi, S. -Y. ; Guo, L. ; et al ( December 2020 , Nature Communications)

   Abstract The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn 3 GaN, in which the triangular spin structure creates a low magnetic symmetry while maintainingmore »a high crystalline symmetry. We demonstrate that epitaxial Mn 3 GaN/permalloy heterostructures can generate unconventional spin-orbit torques at room temperature corresponding to out-of-plane and Dresselhaus-like spin polarizations which are forbidden in any sample with two-fold rotational symmetry. Our results demonstrate an approach based on spin-structure design for controlling spin-orbit torque, enabling high-efficient antiferromagnetic spintronics.« less
4. Magnetic memory driven by topological insulators

   https://doi.org/10.1038/s41467-021-26478-3  

   Wu, Hao ; Chen, Aitian ; Zhang, Peng ; He, Haoran ; Nance, John ; Guo, Chenyang ; Sasaki, Julian ; Shirokura, Takanori ; Hai, Pham Nam ; Fang, Bin ; et al ( October 2021 , Nature Communications)

   Giant spin-orbit torque (SOT) from topological insulators (TIs) provides an energy efficient writing method for magnetic memory, which, however, is still premature for practical applications due to the challenge of the integration with magnetic tunnel junctions (MTJs). Here, we demonstrate a functional TI-MTJ device that could become the core element of the future energy-efficient spintronic devices, such as SOT-based magnetic random-access memory (SOT-MRAM). The state-of-the-art tunneling magnetoresistance (TMR) ratio of 102% and the ultralow switching current density of 1.2 × 10⁵ A cm⁻²have been simultaneously achieved in the TI-MTJ device at room temperature, laying down the foundation for TI-driven SOT-MRAM. Themore »charge-spin conversion efficiencyθ_SHin TIs is quantified by both the SOT-induced shift of the magnetic switching field (θ_SH = 1.59) and the SOT-induced ferromagnetic resonance (ST-FMR) (θ_SH = 1.02), which is one order of magnitude larger than that in conventional heavy metals. These results inspire a revolution of SOT-MRAM from classical to quantum materials, with great potential to further reduce the energy consumption.

   « less
5. Exchange biased anomalous Hall effect driven by frustration in a magnetic kagome lattice

   https://doi.org/10.1038/s41467-020-14326-9  

   Lachman, Ella ; Murphy, Ryan A. ; Maksimovic, Nikola ; Kealhofer, Robert ; Haley, Shannon ; McDonald, Ross D. ; Long, Jeffrey R. ; Analytis, James G. ( January 2020 , Nature Communications)

   Co$$_{3}$$${}_3$Sn$$_{2}$$${}_2$S$$_{2}$$${}_2$is a ferromagnetic Weyl semimetal that has been the subject of intense scientific interest due to its large anomalous Hall effect. We show that the coupling of this material’s topological properties to its magnetic texture leads to a strongly exchange biased anomalous Hall effect. We argue that this is likely caused by the coexistence of ferromagnetism and geometric frustration intrinsic to the kagome network of magnetic ions, giving rise to spin-glass behavior and an exchange bias.