Ferromagneticlike states and all-optical 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 the s-d exchange interaction. The dynamics of the localized and itinerant spins is described by coupled rate equations, which include electron-phonon interaction, spin-lattice relaxation, and exchange scattering, induced by the s-d exchange interaction. The exchange scattering leads to the formation of ferromagneticlike states at initial temperatures T both below and above the magnetization compensation temperature T-M with the opposite polarities in these two temperature regions. Inclusion of electron-phonon interaction and spin-lattice relaxation in the dynamical equations leads to the switching in a temperature range 0 < T < T-f, where T-f is slightly higher than T-M and strongly depends on the spin-lattice relaxation time of itinerant electrons. The switching requires less pulse fluence in the vicinity of T-M.