Magnetic aftereffect in spring magnets and the Preisach model of hysteresis

Magnetic viscosity measurements on NdFeB spring-magnets are interpreted by means of a thermodynamic generalization of the Preisach hysteresis model. The model correctly predicts the observed decay of magnetization and clarifies the connection between anomalous, non-monotone after-effect and applied field history. Comparison between theory and experiments permits one to estimate the after-effect activation volume, d/sup 3//spl ap/(12 nm)/sup 3/, and the attempt frequency 1//spl tau//sub v/ /spl sim/10/sup 10/ s/sup -1/.