Abstract
The large spin Hall effect in topological insulators (TIs) is very attractive for ultralow-power spintronic devices. However, evaluation of the spin Hall angle and spin–orbit torque (SOT) of TIs is usually performed on high-quality single-crystalline TI thin films grown on dedicated III-V semiconductor substrates. Here, we report on room-temperature ultralow power SOT magnetization switching of a ferrimagnetic layer by non-epitaxial BiSb TI thin films deposited on Si/SiO2 substrates. We show that non-epitaxial BiSb thin films outperform heavy metals and other epitaxial TI thin films in terms of the effective spin Hall angle and switching current density by one to nearly two orders of magnitude. The critical SOT switching current density in BiSb is as low as 7 × 104 A/cm2 at room temperature. The robustness of BiSb against crystal defects demonstrate its potential applications to SOT-based spintronic devices.
Highlights
The large spin Hall effect in topological insulators (TIs) is very attractive for ultralow-power spintronic devices
The spin–orbit torque (SOT) magnetization switching was performed by sweeping an in-plane external magnetic field Hx under a constant direct currents (DC) current, or sweeping a DC/pulse current under a constant Hx
We have demonstrated ultralow power room-temperature SOT magnetization switching induced by non-epitaxial
Summary
The large spin Hall effect in topological insulators (TIs) is very attractive for ultralow-power spintronic devices. We report on room-temperature ultralow power SOT magnetization switching of a ferrimagnetic layer by non-epitaxial BiSb TI thin films deposited on Si/SiO2 substrates. Charge-to-spin conversion utilizing the strong spin–orbit coupling (SOC) in non-magnetic materials has become a very attractive concept with possible applications to various spintronic devices, such as spin–orbit torque (SOT) magnetoresistive random access memories (MRAM), race-track m emories, and spin torque nano-oscillators. In SOT-based devices, a perpendicular pure spin current density Js is generated by an in-plane charge current density Je in the non-magnetic layer through the spin Hall effect (SHE), whose charge-to-spin conversion efficiency is characterized by the spin Hall angle θSH = (2e/ħ) Js/Je. finding spin Hall materials with large θSH and high electrical conductivity is crucial for SOT applications, and there have been huge efforts so far to achieve that goal. A giant unidirectional spin Hall magnetoresistance of 1.1%, which is three orders of magnitude larger than in those in metallic bilayers, has been observed in a BiSb/ GaMnAs bilayer
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