A MODEL THAT GIVES RISE TO EFFECTIVE DRY FRICTION IN MICROMAGNETICS

Since dissipation requires motion, the velocity-independent friction o f macroscopic systems must result from quick motions of some of its co mponents. A model of coupled spins, some of which have irregular aniso tropy directions, presents velocity independent loss. During a collect ive motion of the spin ensemble, an irregular spin can fall into its p otential minimum, from which it is subsequently dragged out again. The effect is pronounced for a range of the ratio between the anisotropy and interatomic exchange coupling constants which is typical for rare- earth ions.