Light and microwave driven spin current detection in FeGaB thin films*

Measurements of frequency dependent ferromagnetic resonance (FMR), spin pumping driven dc voltage (V_dc) and femtosecond light-pulse-induced terahertz (THz) emission are reported for amorphous films of Fe₇₈Ga₁₃B₉ (FeGaB) alloy to address the phenomenon of self-induced inverse spin Hall effect (ISHE) in plain films of metallic ferromagnets. The asymmetric V_dc signal draws contributions from rectification effects of a ≈ 0.4 % anisotropic magnetoresistance and a large (≈ 54 nΩ.m) anomalous Hall resistivity (AHR) [1] of these films which ride over the effect of spin – orbit coupling driven spin-to-charge conversion near the film – substrate interface. The femtosecond light-pulse-induced THz emission experiments reveal a decreasing THz signal with increasing FeGaB thickness. This study will be very useful for fully understanding the spin pumping induced dc voltages in metallic ferromagnets with disordered interfaces and large anomalous Hall effect.

[1] Harder, Michael et al. Physics Reports 661 (2016): 1-59.