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

Abstract

Polycrystalline single-phase europium iron garnet films (EuIG, Eu3Fe5O12, a ferrimagnetic insulator), with thicknesses from 25 to 50 nm and roughness <1 nm, have been grown on various substrates using pulsed laser deposition followed by a rapid thermal anneal. The films are under strain that originates primarily from thermal mismatch and leads to a magnetoelastic anisotropy that dominates the net anisotropy. EuIG grown on quartz (0001) demonstrated perpendicular magnetic anisotropy (PMA) attributed to the in-plane (IP) compressive thermal mismatch strain, whereas films on (11 2¯ 0) quartz, Si, fused silica, and yttria-stabilized zirconia exhibited an IP easy axis due to tensile strain, consistent with the positive magnetostriction of polycrystalline EuIG. For the PMA EuIG, the saturation magnetization was close to that of bulk EuIG, and the out-of-plane coercivity ranged from 600 to 900 Oe, depending on the film thickness. Spin transport measurements on Pt/EuIG/quartz heterostructures gave an anomalous Hall effect-like spin Hall magnetoresistance similar to that of Pt/epitaxial single crystal EuIG. These results show that high quality polycrystalline garnets can be grown with PMA making them useful for applications in spintronic devices.