Spin-current generation and Spin-Orbit Torque switching in Perpendicularly Magnetized Insulating Ni_0.65Zn_0.35Fe_1.2Al_0.8O₄films

Perpendicular magnetic anisotropy (PMA) and low magnetic damping are key features in developing next-generation spin-torque based technologies. In this talk, we demonstrate PMA as well as low damping in spinel ferrite Ni_0.65Zn_0.35Fe_1.2Al_0.8O₄ (NZAFO) films grown on (001)-oriented MgGa₂O₄ (MGO) substrates under tensile strain. Structural characterization indicates epitaxial growth of NZAFO on MGO with excellent crystallinity and mosaic spread Δω ~ 0.06°. Bulk SQUID magnetometry indicates an out-of-plane magnetic easy axis with a coercivity as low as 2 mT in films of thickness ~10-20 nm. Ferromagnetic resonance with an out-of-plane field reveals narrow linewidths on the order of 1 mT and Gilbert damping parameters of α ≈ 5-9×10^-4, significantly lower than previous studies. These damping values are some of the lowest reported to date for a ferromagnetic insulator with PMA. We will incorporate NZAFO with Pt in bilayers to study spin pumping and spin-orbit torque switching. NZAFO can be coherently interfaced with other spinels as well as other oxides, and therefore holds great promise for future spin current-based applications.