Ultrafast heating-induced magnetization switching in ferrimagnets

We study theoretically the light-induced magnetization switching in a binary ferrimagnet of the type A(p)B(1-p), 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 tau(s). 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 tau(s). For long tau(s) the switching occurs only below the magnetisation compensation temperature T-K. For physically reasonable values of tau(s) this temperature range extends from 0 K to T-f (tau(s)), where T-f (tau(s)) is slightly higher than the compensation temperature T-K. With further decrease of tau(s) this temperature range shifts to temperatures higher than T-K.