Ultrafast heating-induced magnetization switching in ferrimagnets

Abstract

We study theoretically the light-induced magnetization switching in a binary ferrimagnet of the type , randomly occupied by two different species of magnetic ions. The localized spins are coupled with spins of itinerant electrons via s-d exchange interaction. Model parameters are chosen so that to achieve similarity between magnetic characteristics of the model and those of ferrimagnetic rare-earth-transition metal GdFeCo alloys. The switching is triggered by heating of the itinerant electrons by a laser pulse. The spin dynamics is governed by the cooling of itinerant electrons, exchange scattering, induced by the s-d exchange interaction and spin-lattice relaxation of the itinerant spins with a characteristic time . The dynamics of the localized and itinerant spins is described by coupled rate equations. The main conclusion of this study is that the switching occurs only in a certain temperature range depending on . For long the switching occurs only below the magnetisation compensation temperature TK. For physically reasonable values of this temperature range extends from 0 K to , where is slightly higher than the compensation temperature TK. With further decrease of this temperature range shifts to temperatures higher than TK.