Spin-orbit torque switching in 2D ferromagnet / topological insulator heterostructure grown by molecular beam epitaxy

TL;DR

This study demonstrates that atomically smooth van der Waals heterostructures of topological insulators and ferromagnets grown by molecular beam epitaxy enable efficient, low-power spin-orbit torque switching with minimal device variation.

Contribution

We developed a high-quality van der Waals heterostructure of TI and FM via molecular beam epitaxy, achieving reliable, low-current magnetization switching with minimal device-to-device variation.

Findings

Magnetization switching with current density Jc < 10^10 A/m^2

High crystalline quality and low variation across devices

Effective SOT manipulation in 2D heterostructures

Abstract

Topological insulators (TIs) are a promising class of materials for manipulating the magnetization of an adjacent ferromagnet (FM) through the spin-orbit torque (SOT) mechanism. However, current studies combining TIs with conventional FMs present large device-to-device variations, resulting in a broad distribution of SOT magnitudes. It has been identified that the interfacial quality between the TI and the FM is of utmost importance in determining the nature and efficiency of the SOT. To optimize the SOT magnitude and enable ultra-low-power magnetization switching, an atomically smooth interface is necessary. To this end, we have developed the growth of a full van der Waals FM/TI heterostructure by molecular beam epitaxy. The compensated TI (Bi0.4Sb0.6)2Te3 and ferromagnetic Fe3GeTe2 (FGT) were chosen because of their exceptional crystalline quality, low carrier concentration in BST and relatively large Curie temperature and perpendicular magnetic anisotropy in FGT. We characterized the magnitude of the SOTs by using thorough harmonic magnetotransport measurements and showed that the magnetization of an ultrathin FGT film could be switched with a current density Jc < 10^10 A/m^2. In comparison to previous studies utilizing traditional FMs, our findings are highly reliable, displaying little to no variation between devices.