Spin Pumping in Epitaxial Ge1‐xSnx Alloys

The use of Ge1-xSnx semiconductor alloys is generating significant interest in the scientific community due to their precisely tunable Sn content. This tunability makes them particularly attractive for applications in photonics, electronics, and, more recently, spintronics. Room-temperature emission and detection of spin currents are observed in Ge1-xSnx/Co hybrids through spin-pumping ferromagnetic resonance. Experiments conducted over a wide range of compositions and strains show that spin current injection is enhanced in Ge1-xSnx solid solutions compared to elemental Ge. The magnetization dynamics reveal an intriguing scenario where the Gilbert damping constant and the spin mixing conductance display a non-monotonic behavior. The maximum spin-pumping efficiency occurs at a Sn molar fraction of ≈10 at.% and remains unaffected by the elastic strain built up in Ge1-xSnx films through epitaxial growth on Ge-buffered Si substrates. These findings highlight the non-trivial dependence of alloy scattering in defining spin accumulation and relaxation mechanisms, providing insightful information on phenomena at the forefront of spintronics and quantum technology research.