MODEL OF THERMALLY ACTIVATED MAGNETIZATION REVERSAL IN THIN-FILMS OF AMORPHOUS RARE-EARTH-TRANSITION-METAL ALLOYS

Monte Carlo simulations on a two-dimensional lattice of magnetic dipol es have been performed to investigate the magnetic reversal by thermal activation in rare-earth-transition-metal (RE-TM) alloys. Three mecha nisms of magnetization reversal were observed: nucleation dominated gr owth, nucleation followed by the growth of magnetic domains containing no seeds of unreversed magnetization, and nucleation followed by dend ritic domain growth by successive branching in the motion of the domai n walls. The domain structures are not fractal; however, the fractal d imension of the domain wall was found to be a good measure of the jagg edness of the domain boundary surface during the growth process. The e ffects of the demagnetizing field on the hysteretic and time-dependent properties of the thin films were studied and some limitations in the application of the Fatuzzo model on magneto-optic media are identifie d.