Perpendicular magnetic anisotropy and spin mixing conductance in polycrystalline europium iron garnet thin films

Rare earth iron garnets (REIG) are a diverse class of magnetic insulators in which properties such as the anisotropy and magnetostriction can be tuned by choice of rare earth ion. Garnet films with perpendicular magnetic anisotropy (PMA) are attractive for studies of spin orbit torque and chiral spin textures. PMA has been achieved in epitaxial REIG on garnet substrates due to magnetoelastic anisotropy from epitaxial lattice mismatch strain, but for making devices on non-garnet substrates, PMA without epitaxy is essential. Here we report the growth and properties of polycrystalline europium iron garnet (EuIG) with PMA. Films were grown by pulsed laser deposition followed by a rapid thermal anneal. Films on quartz (0001) substrates demonstrated PMA attributed to the in-plane compressive thermal mismatch strain, whereas films on (11-20) quartz, Si, and fused SiO₂ exhibited an in-plane easy axis due to tensile strain, consistent with the positive magnetostriction of EuIG. Spin transport measurements on Pt/EuIG/quartz heterostructures gave an anomalous Hall effect-like spin Hall magnetoresistance and spin mixing conductance similar to single crystal epitaxial EuIG. These results show that polycrystalline garnet can be grown with PMA, making it useful for applications in spintronics.