We develop an atomistic spin-lattice-dynamics model for simulating energy relaxation in magnetic materials. The model explicitly solves equations of motion for the atoms and spins, and includes interaction with electron excitations. We apply the model to simulate the dynamics of propagation of a compressive elastic wave in iron. We find that coupling between the lattice, spin, and electron degrees of freedom does not have an appreciable effect on the velocity of the wave. At the same time, dissipative lattice-electron-spin interactions entirely dominate the dynamics of attenuation of the wave in the material.
