Ferromagnetic domain distribution in thin films during magnetization reversal

It is shown that polarized neutron reflectometry can determine in a model-free way not only the mean magnetization of a ferromagnetic thin film at any point of a hysteresis cycle, but also the mean-square dispersion of the magnetization vectors of its lateral domains. This technique is applied to elucidate the mechanism of magnetization reversal of an exchange-biased Co/CoO bilayer. The reversal process above the blocking temperature $T_b$ is governed by uniaxial domain switching, while below $T_b$ the reversal of magnetization for the trained sample takes place with substantial domain rotation.