凝聚态物理
拓扑绝缘体
磁电阻
材料科学
自旋电子学
自旋霍尔效应
无定形固体
自旋极化
电子
铁磁性
物理
磁场
化学
结晶学
量子力学
作者
Federico Binda,Stefano Fedel,S. F. Alvarado,Paul Noël,Pietro Gambardella
标识
DOI:10.1002/adma.202304905
摘要
Topological insulators have attracted great interest as generators of spin-orbit torques (SOTs) in spintronic devices. Bi1 - x Sbx is a prominent topological insulator that has a high charge-to-spin conversion efficiency. However, the origin and magnitude of the SOTs induced by current-injection in Bi1 - x Sbx remain controversial. Here we report the investigation of the SOTs and spin Hall magnetoresistance resulting from charge-to-spin conversion in twin-free epitaxial layers of Bi0.9 Sb0.1 (0001) coupled to FeCo, and compare it with that of amorphous Bi0.9 Sb0.1 . We find a large charge-to-spin conversion efficiency of 1 in the first case and less than 0.1 in the second, confirming crystalline Bi0.9 Sb0.1 as a strong spin injector material. The SOTs and spin Hall magnetoresistance are independent of the direction of the electric current, indicating that charge-to-spin conversion in single-crystal Bi0.9 Sb0.1 (0001) is isotropic despite the strong anisotropy of the topological surface states. Further, we find that the damping-like SOT has a non-monotonic temperature dependence with a minimum at 20 K. By correlating the SOT with resistivity and weak antilocalization measurements, we conclude that charge-spin conversion occurs via thermally-excited holes from the bulk states above 20 K, and conduction through the isotropic surface states with increasing spin polarization due to decreasing electron-electron scattering below 20 K. This article is protected by copyright. All rights reserved.
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