Giant widening of interface magnetic layer in almost compensated iron garnet

Abstract

A two-sublattice ferrimagnet undergoes a transition from a collinear to the canted magnetic phase at magnetic field oriented along an easy magnetization direction. In this work, we study the transition by means of the magneto-optical Faraday effect in a thin film of compensated iron garnet (Lu3− xBi x)(Fe5− y−zGa yAl z)O12 grown on the Gd3Ga5O12 substrate. In the immediate vicinity of the compensation temperature, a precursor of the transition with a complex shape was observed. Using a special sample with variable thickness, we demonstrate an interfacial origin of the precursor. Diffusion of gadolinium from the substrate into the film forms a thin intermixed layer with enhanced magnetization. It induces an extended inhomogeneous magnetic structure in the film. A two-step shape of the precursor appears due to an easy-plane anisotropy of the intermixed magnetic layer. We emphasize that an effective width of the inhomogeneous magnetization distribution in the film grows enormously while approaching the compensation temperature.