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تسجيل مستخدم جديدA conductive topological insulator with colossal spin Hall effect for ultra-low power spin-orbit-torque switching
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Spin-orbit-torque (SOT) switching using the spin Hall effect (SHE) in heavy metals and topological insulators (TIs) has great potential for ultra-low power magnetoresistive random-access memory (MRAM). To be competitive with conventional spin-transfer-torque (STT) switching, a pure spin current source with large spin Hall angle (${theta}_{SH}$ > 1) and high electrical conductivity (${sigma} > 10^5 {Omega}^{-1}m^{-1}$) is required. Here, we demonstrate such a pure spin current source: BiSb thin films with ${sigma}{sim}2.5*10^5 {Omega}^{-1}m^{-1}$, ${theta}_{SH}{sim}52$, and spin Hall conductivity ${sigma}_{SH}{sim}1.3*10^7 {hbar}/2e{Omega}^{-1}m^{-1}$ at room temperature. We show that BiSb thin films can generate a colossal spin-orbit field of 2770 Oe/(MA/cm$^2$) and a critical switching current density as low as 1.5 MA/cm$^2$ in Bi$_{0.9}$Sb$_{0.1}$ / MnGa bi-layers. BiSb is the best candidate for the first industrial application of topological insulators.
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Precise estimation of spin Hall angle as well as successful maximization of spin-orbit torque (SOT) form a basis of electronic control of magnetic properties with spintronic functionality. Until now, current-nonlinear Hall effect, or second harmonic
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onic states have been extensively pursued to realize efficient spin-orbit torque (SOT) switching. However, so far current-induced magnetic switching with TI has only been observed at cryogenic temperatures. It remains a controversial issue whether the topologically protected electronic states in TI could benefit spintronic applications at room temperature. In this work, we report full SOT switching in a TI/ferromagnet bilayer heterostructure with perpendicular magnetic anisotropy at room temperature. The low switching current density provides a definitive proof on the high SOT efficiency from TI. The effective spin Hall angle of TI is determined to be several times larger than commonly used heavy metals. Our results demonstrate the robustness of TI as an SOT switching material and provide a direct avenue towards applicable TI-based spintronic devices.
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