Spin excitations in a monolayer scanned by a magnetic tipM. P. Magiera1, L. Brendel1, D. E. Wolf1 and U. Nowak2
1 Department of Physics and CeNIDE, University of Duisburg-Essen - D-47048 Duisburg, Germany, EU
2 Theoretical Physics, University of Konstanz - D-78457 Konstanz, Germany, EU
received 20 April 2009; accepted in final form 30 June 2009; published July 2009
published online 29 July 2009
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 polarisation cloud dragged along with the tip.
68.35.Af - Atomic scale friction.
75.10.Hk - Classical spin models.
75.70.Rf - Surface magnetism .
© EPLA 2009