  Energy dissipation via spin excitations is investigated for a hard
ferromagnetic tip scanning a soft magnetic monolayer. We use the classical
Heisenberg model with Landau-Lifshitz-Gilbert (LLG)-dynamics including a
stochastic field representing finite temperatures. The friction force depends
linearly on the velocity (provided it is small enough) for all temperatures.
For low temperatures, the corresponding friction coefficient is proportional to
the phenomenological damping constant of the LLG equation. This dependence is
lost at high temperatures, where the friction coefficient decreases
exponentially. These findings can be explained by properties of the spin
polarization cloud dragged along with the tip.
