Dynamic phase transitions in thin ferromagnetic films

Abstract

Monte Carlo simulations have been used to investigate the dynamic phase behavior of a classical Heisenberg spin system with a bilinear exchange anisotropy \ensuremath{\Lambda} in a planar thin film geometry. Studies of the field amplitude, frequency, and temperature dependence show dynamic phase transitions in films subject to a pulsed oscillatory external field. Thin films with competing surface fields show separate and distinct dynamic phase transitions for the bulk and surface layers of the film. Between the two transitions, a mixed state with coexisting dynamically ordered and dynamically disordered phases is observed in the film. In contrast, the free film with no surface fields show a single dynamic phase transition as in a bulk system.