Spin dependent transport in ferromagnetic high-entropy-alloy thin films

高梨 弘毅

Takanashi, Koki

High-entropy alloys (HEAs) have attracted considerable attention, however, most of studies have been conducted using bulk magnets, and the spin-dependent transport in ferromagnetic HEA thin films have not been well investigated. In this study, we focus on FeCoNiCuPd HEAs, which exhibit a Curie temperature higher than room temperature and contain a heavy element (Pd) with relatively large spin-orbit interaction. The thin-film samples with different composition ratios of Cu and Pd under the same amount of FeCoNi, FeNiCoCuPd (0X+Y40), were prepared on thermally oxidized Si substrates at an ambient temperature by an ultrahigh vacuum sputtering system. All the films exhibited ferromagnetic hysteresis curves with soft magnetic behavior at room temperature. The saturation magnetization increased linearly with the Pd concentration, which might be attributed mainly to the induced Pd moment. Anisotropic magnetoresistance effect (AMR) and anomalous Hall effect (AHE) were measured for Hall-bar devices fabricated by conventional photolithography and Ar milling process. The MR ratio and the anomalous Hall conductivity showed a smooth, simple increase with the Pd concentration, suggesting that the spin-orbit interaction of constituent elements plays a significant role on the AMR and the AHE in ferromagnetic HEAs.