SPIN DYNAMICS IN MAGNETS - EQUATION-OF-MOTION AND FINITE-TEMPERATURE EFFECTS

General equations of motion are introduced for the evaluation bf spin dynamics in magnetic materials. The theory uses the adiabatic separati on oi diagonal and off-diagonal components of the spin density matrix: This adiabatic approach considers the orientation of the local magnet ic moments to be slowly varying relative to, their magnitudes. The ang les of the magnetization density are introduced as collective variable s in density functional theory. The equations and technique can be sim ultaneously combined with those of first-principles molecular dynamics for the consistent treatment of spin-lattice interactions. Stochastic and deterministic approaches for treating finite temperature effects are introduced for such dynamics. The method is implemented within the local density approximation and applied to gamma-Fe, a frustrated sys tem where we obtain additional low-energy magnetic configurations.