Gilbert damping in polycrystalline thin films

Damped gyromagnetic precession equations are discussed and solutions of a single-spin system are illustrated. A brief description of our variational finite element model of magnetisation dynamics is then given. The reversal of an isolated Voronoi grain is investigated and its response to the applied magnetic field is shown to vary with the damping parameter in a manner that is somewhat different to the single-spin system, thus highlighting the need for sub-grain discretisation. Implicit periodic boundary conditions are enforced around an ensemble of Voronoi grains to simulate the effects of damping in a polycrystalline thin film. This reveals that damping influences not only the speed, but also the mode of magnetisation reversal. The minimum of magnetisation reversal time is shown to occur at the same value of the damping parameter in all three systems.