Engineering Easy-plane Anisotropy in Ferrimagnetic Rare-earth Iron Garnet

Rare-earth iron garnets, a ferrimagnetic insulator, have received attention for their many properties including small damping and tunable magnetization and angular momentum compensation temperatures. Most research efforts have been focused on garnet thin films grown on the (111) plane because of their perpendicular magnetic anisotropy (PMA), and the in-plane anisotropy, however neglected, can be important for our understanding of the switching behavior and the energetics of magnetic textures. In-plane anisotropy can be conveniently explored in garnet thin films on (110) planes. Here we combine a theoretical and experimental analysis of the anisotropy landscape for Europium iron garnet (EuIG) epitaxially grown on (110) Gadolinium Gallium garnet (GGG) using pulsed laser deposition.



The angular dependence of anisotropy is calculated by combining the individual contributions including magnetocrystalline anisotropy, magnetoelastic anisotropy, shape anisotropy and growth-induced anisotropy, which may contribute for non-ideal stoichiometry. This predicts an easy axis out of plane along [110], with hard and intermediate axes in plane along [001] and [-110] respectively. The anisotropy landscape is probed with vibrating sample magnetometry (VSM) and spin-Hall magnetoresistance (SMR) measurements. The SMR result is simulated and fitted to a Stoner-Wohlfarth model. The experimental measurements yield the expected hard and easy axes, The unexpected hysteresis when external magnetic field is swept along the intermediate anisotropy axis is well explained by the modification of anisotropy landscape by the cubic symmetric magneto-crystalline anisotropy. Both the in-plane anisotropy and out-of-plane anisotropy are shown to be tuned with film thickness, with a change in easy-axis from [110] to [-110] with increasing thickness. Understanding and control of this anisotropy landscape could enable many possible fundamental studies and applications.