Misfit dislocations and spin pumping in epitaxial Fe/Rh bilayers

Efficient spin to charge conversion is a key property of magnetic materials and heterostructures for further devel- opment of energy-efficient spintronic devices. We investigate Rh as a heavy 4d metal paramagnet in heterostruc- tures with Fe films and demonstrate its high spin-mixing conductance for Fe/Rh bilayers grown on GaAs(001) and GaAs(110) substrates. Our studies combined in situ low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), cross-sectional transmission electron microscopy (TEM), and allowed us to conclude that the Fe/Rh interface is epitaxial and atomically sharp despite of 6% lattice mismatch. We determined interfacial defects and characterise strain in Fe and Rh by employing geometric phase analysis (GPA). Using broadband ferromagnetic resonance, we find a significant spin pumping efficiency in Fe/Rh with a spin-mixing conductance comparable to that of Fe/Pt bilayers while showing a spin diffusion length similar to Pd.