Perpendicular magnetic anisotropy in ultrathin yttrium iron garnet films prepared by pulsed laser deposition technique

Abstract

A series of thin and ultrathin (<500 A thick) polycrystalline yttrium iron garnet (YIG) films has been prepared on quartz substrates by the pulsed laser deposition technique to study the effects of dimensional changes on the magnetic properties. The film thickness was varied from 100 to 3800 A. Saturation magnetization decreased rapidly in ultrathin films with decreasing thickness. The lattice cell of all samples was found to be slightly distorted though the elementary cell volume was one of a bulk crystal. The Curie temperature of the films did not differ from the bulk YIG value. Ferromagnetic resonance experiments show evidence of a change from in-plane magnetization to a perpendicular magnetization in films thinner than 140 A. This reorientation can be explained by the magnetoelastic anisotropy contribution related to thermally induced strain. This contribution is likely to be the principal origin of the perpendicular anisotropy.