Microscopic model for ultrafast magnetization dynamics of multisublattice magnets

We introduce a microscopic model to describe the ultrafast response of magnetic materials with two sublattices to heating by a femtosecond laser pulse. Even though the model is based on a set of simple Hamiltonians, it readily reproduces experimental observations such as ultrafast reversal of ferrimagnets and delayed demagnetization of one sublattice in ferromagnetic alloys. The calculations give insight into the microscopic mechanisms and thermodynamics governing the complex dynamics of these multisublattice magnets.