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

Abstract

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.

Direct‐Contact Seebeck‐Driven Transverse Magneto‐Thermoelectric Generation in Magnetic/Thermoelectric Bilayers

“…While not considered during the formulation of the expressions, this interfacial layer could contribute positively to ρ AHE,eff and $$S_{{\mathrm{tot}}}^y$$, due to the emergence of spin‐orbit coupling at the interface or ferromagnetic surface state of FeSi. [ 49,50 ] If the thicknesses of the bilayers are increased, it is possible that the interfacial layer would have a less significant influence on the transport properties, leading to a better agreement between the experimental and calculated results. On the other hand, if the thicknesses of the bilayers are increased to a level that they are comparable to the sample size in the x ‐ y plane ( L and W ), the assumption for the modeling is no longer satisfied and the derived expressions cannot accurately describe the transverse thermopower of the bilayers.…”