Ultralow Power Magnetization Switching by Non‐Epitaxial Topological Insulator‐Generated Spin–Orbit Torque

Abstract

Topological insulators (TIs) with large spin Hall effect have potential applications for ultralow power consumption spintronic devices. However, the present methods for fabricating TIs mainly rely on epitaxial methods, which limits their mass production. Herein, perpendicular magnetized Pt/Co/(Bi1–x Sb x )2Te3 (BST) heterostructures are prepared to measure the spin–orbit torque efficiency of BST fabricated by the conventional magnetron sputtering method, which shows large‐scale wafer production ability. The Fermi levels and the topological surface states (TSSs) are modulated by the composition of Sb in BST. The effective damping‐like spin Hall angle (θ SH eff ) is independent of the thickness of TIs. When the Fermi level is near the Dirac point, θ SH eff for these non‐epitaxial heterostructures reaches its maximum value around 0.77, which is much larger than that of traditional ferromagnetic/heavy metal (FM/HM) heterostructures and quite close to that of the epitaxial TIs. This indicates that the TSS has the dominant contribution to θ SH eff . The large θ SH eff results in the small critical current density (J c ≈ 105 A cm−2) for fully switching the magnetization of Co, compared with FM/HM heterostructures with J c around 107 A cm−2. This work paves the way for potential large‐scale spintronic devices using low energy consumption non‐epitaxial TIs.

Spintronic devices based on topological and two-dimensional materials

“…[52] 率先使用磁控溅射技术沉积了 Bi x Se 1-x 薄膜拓扑绝缘体材料并且获取巨大的SHA, 此外该工作也实现了室温SOT翻转. 溅射多晶 Bi 2 Se 3 也被证明可以产生大的θ SH , 同时实现较低 的临界翻转电流密度 [60][61][62][63][64] . 溅射薄膜方法可能是 当前半导体制造中采用的实用方法之一.…”