Correlation of hysteresis loop and domain structure of CoFeB/Pd multilayer at various temperatures

Temperature-dependent magnetic hysteresis loop, magnetic relaxation, and magnetic domain behavior of (4 angstrom CoFeB/10 angstrom Pd)(4) multilayer were investigated by means of magneto-optical Kerr microscopy, where the hysteresis, relaxation, and domain structures are simultaneously observed on the same area from room temperature up to 450 K near the Curie temperature of the multilayer. Below 380 K, the hysteresis loops are found to have squareness about 1, while the loops become more slanted and eventually paramagnetic at temperatures higher than 430 K. Correspondingly, the magnetic domain patterns exhibit transitional behavior from a circular to dendritic structure with change of relative ratio between the reversed and non-reversed sub-domain areas with respect to the temperature.