A Noble-Metal-Free Spintronic System with Proximity-Enhanced Ferromagnetic Topological Surface State of FeSi above Room Temperature

Strongly spin-orbit coupled states at metal interfaces, topological insulators, and 2D materials enable efficient electric control of spin states, offering great potential for spintronics. However, there are still materials challenges to overcome, including the integration into advanced silicon electronics and the scarce resources of constituent heavy elements of those materials. Through magneto-transport measurements and first-principles calculations, here robust spin-orbit coupling (SOC)-induced properties of a ferromagnetic topological surface state in FeSi and their controllability via hybridization with adjacent materials are demonstrated. In comparison to the case of its naturally oxidized surface, the ferromagnetic transition temperature is greatly increased beyond room temperature and the effective SOC strength is almost doubled at the surface in proximity to a wide-bandgap fluoride insulator. Those enhanced magnetic properties enable room-temperature magnetization switching, being applicable to spin-orbit torque based spintronic devices. Realization of strong SOC in the noble-metal-free silicon-based compound will accelerate spintronic applications.

Automated summary

Strongly spin-orbit coupled states in metal interfaces, topological insulators, and 2D materials have great potential for spintronics. However, there are still challenges in integrating them into silicon electronics and dealing with the scarcity of constituent heavy elements. This study demonstrates robust spin-orbit coupling properties of a ferromagnetic topological surface state in FeSi and their controllability through hybridization with adjacent materials. The enhanced magnetic properties enable room-temperature magnetization switching, making it applicable for spin-orbit torque-based spintronic devices.