Thickness-dependent spin pumping in YIG/W90Ti10 bilayers

Abstract

We investigate the spin-pumping efficiency in YIG/W90Ti10 bilayers by measuring the thickness dependence of both the YIG and WTi layers by broadband ferromagnetic resonance (FMR) spectroscopy. The deposition of a 5 nm WTi layer leads to enhanced Gilbert damping in thinner YIG films, indicating efficient spin-current injection. From the spin-pumping contribution to the damping of the YIG/WTi bilayer, we determine an effective spin-mixing conductance of 3.3 × 1018 m−2 for the 5 nm WTi layer. Further measurements with varying WTi thickness reveal a non-monotonic dependence of spin-mixing conductance, peaking at 4.2 × 1018 m−2 for a 3 nm WTi layer. This behavior may be attributed to the chemical and structural phase transition in the WTi layer. Furthermore, comparative analysis with YIG/W bilayers shows that Ti doping significantly reduces geff↑↓. These findings highlight the critical role of alloy composition and structural phase in tuning spin transport for spintronic applications.