Comparative Study of Spin Pumping in Epitaxial- and Polycrystalline-NiO/Ni80Fe20

Abstract

We perform a comparative study of spin pumping in NiO/Ni[Formula: see text]Fe[Formula: see text] (Py) by altering the crystallinity of NiO. We simultaneously grow high-quality NiO/Py heterostructures on Si/SiO2 and Al2O3(0001) substrates. Although the growth on Si/SiO2 substrate produced polycrystalline NiO (Poly-NiO), the growth on Al2O3(0001) substrate produced epitaxial NiO (Epi-NiO). Our ferromagnetic resonance measurements reveal the presence of two-magnon scattering (TMS) in the measured linewidth for the Epi-NiO/Py system. By carefully considering the contribution of TMS, we found the effective spin mixing conductance, g[Formula: see text] to be comparable in both Poly-NiO/Py and Epi-NiO/Py, despite the different crystallinity of NiO. Our findings show that g[Formula: see text] of an optimized polycrystalline-NiO/Py system can reach the value for an epitaxial-NiO/Py system.