Alloying-Controlled Tuning of Interfacial Spin-Orbit Interaction and Magnetic Damping in Crystalline FeCo Thin Films Grown on GaAs(001).

Lao, Hongrui; Kronseder, Matthias; Yuan, Zhe; Narr, Thomas; Meier, Thomas N G; Mundigl, Nadine; Qu, Xianlin; Wang, Zhongchang et al. · Adv Mater · 2026

basic_science · Level V

Where this comes from

Abstract

The discovery of intrinsic spin-orbit fields in non-centrosymmetric ferromagnets have attracted considerable interest for both fundamental studies and technological applications. However, once such materials are synthesized, the strength of the spin-orbit fields is difficult to tune because it is primarily a bulk property. Here, we demonstrate that the interfacial spin-orbit interaction (SOI) in single-crystalline Fe<sub>1-</sub> <sub>x</sub>Co<sub>x</sub> thin films grown on GaAs(001) can be continuously tuned via alloying. Using spin-orbit ferromagnetic resonance, we find that the Landé g-factor, the Gilbert damping α, and the interfacial spin-orbit fields exhibit a common nonmonotonic dependence on Co concentration. A pronounced minimum occurs near x ≈ 0.2 where an ultra-low damping α ≈ 0.0015 is achieved. Furthermore, we observe linear scaling between α and (g - 2)<sup>2</sup>, suggesting that interfacial SOI may also contribute to magnetic relaxation. These results identify alloying as an effective knob to engineer interfacial SOI and damping in single crystalline ferromagnet/semiconductor heterostructures.