Symmetry-dependent field-free switching of perpendicular magnetization
Pennycook, S. J.
KAUST DepartmentMaterial Science and Engineering Program
Physical Science and Engineering (PSE) Division
Spintronics Theory Group
Embargo End Date2021-07-18
Permanent link to this recordhttp://hdl.handle.net/10754/666926
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AbstractModern magnetic-memory technology requires all-electric control of perpendicular magnetization with low energy consumption. While spin–orbit torque (SOT) in heavy metal/ferromagnet (HM/FM) heterostructures1,2,3,4,5 holds promise for applications in magnetic random access memory, until today, it has been limited to the in-plane direction. Such in-plane torque can switch perpendicular magnetization only deterministically with the help of additional symmetry breaking, for example, through the application of an external magnetic field2,4, an interlayer/exchange coupling6,7,8,9 or an asymmetric design10,11,12,13,14. Instead, an out-of-plane SOT15 could directly switch perpendicular magnetization. Here we observe an out-of-plane SOT in an HM/FM bilayer of L11-ordered CuPt/CoPt and demonstrate field-free switching of the perpendicular magnetization of the CoPt layer. The low-symmetry point group (3m1) at the CuPt/CoPt interface gives rise to this spin torque, hereinafter referred to as 3m torque, which strongly depends on the relative orientation of the current flow and the crystal symmetry. We observe a three-fold angular dependence in both the field-free switching and the current-induced out-of-plane effective field. Because of the intrinsic nature of the 3m torque, the field-free switching in CuPt/CoPt shows good endurance in cycling experiments. Experiments involving a wide variety of SOT bilayers with low-symmetry point groups16,17 at the interface may reveal further unconventional spin torques in the future.
CitationLiu, L., Zhou, C., Shu, X., Li, C., Zhao, T., Lin, W., … Chen, J. (2021). Symmetry-dependent field-free switching of perpendicular magnetization. Nature Nanotechnology. doi:10.1038/s41565-020-00826-8
SponsorsThis research is supported by the Singapore National Research Foundation under CRP Award No. NRF-CRP10-2012-02 and the Singapore Ministry of Education MOE2018-T2-1-019 and MOE2018-T2-2-043, A*STAR Grant No. A1983C0036, A*STAR IAF-ICP 11801E0036, MOE Tier1 R-284-000-195-114 and the King Abdullah University of Science and Technology (KAUST). J.S.C. is a member of the Singapore Spintronics Consortium (SG-SPIN).