Spin-orbit torque (SOT) magnetization switching is an efficient method to control magnetization. In SOT switching, controlling a field-like torque strength is indispensable to reduce the critical current density; however, this is difficult because the field-like torque is intrinsic to the material system used. Here, we show that it can be suppressed in a spin-orbit ferromagnet single layer of (Ga,Mn)As by a current-induced Oersted field due to its strong Dresselhaus spin-orbit coupling and non-uniform current distribution. We obtained an extremely low switching current density of 4.6×10^4 A/cm^2, three orders of magnitude smaller than that observed in typical metal bilayers.
Topological insulators (TIs) have attracted much attention due to the gapless metallic surface states (SSs) that are protected by the time-reversal symmetry (TRS). The SSs are promising particularly because of the giant spin-charge current conversion efficiencies. However, because the SSs of TIs are protected by the TRS, they are easily broken when a ferromagnetic material is deposited on the surface of TIs due to a magnetic perturbation. Meanwhile, the SSs in topological crystalline insulators (TCIs) are protected by the mirror reflection symmetry of the crystal. Thus, the influence of the breaking of the TRS by the magnetic perturbation is different in TCIs from that in other TIs. SnTe is a typical and promising TCI. The strong spin-orbit coupling in bulk SnTe is also attractive for spintronic applications. However, there have been no reports of successful spin injection into either the SSs or the bulk state of SnTe. In this study, using a high-quality epitaxial (001)-oriented Fe/ SnTe/ CdTe/ ZnTe heterostructure grown on GaAs, we have successfully observed the inverse spin Hall effect in SnTe induced by spin pumping. A relatively large spin Hall angle of ~0.01 was obtained for bulk SnTe at room temperature. This large value may be partially caused by the surface states. Our result suggests that SnTe can be used for efficient spin-charge current conversion. [S. Ohya et al., Phys. Rev. B 96, 094424 (2017).] This work was supported by Grants-in-Aid for Scientific Research and Spintronics Research Network of Japan (Spin-RNJ).
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