Frequency dependence of magnetization reversal in thin Fe(100) films

We have studied the magnetization reversal of epitaxial Fe(100) films in an ac magnetic field as a function of frequency between 0.1 and 1.2 MHz by polarized neutron reflectivity. Different modes of magnetization reversal are excited depending on the ac field frequency, those with domain nucleation and propagation, and those with a coherent magnetization rotation. At low frequencies the magnetization follows the external field adiabatically via nucleation and propagation of antiparallel 180[degrees] domains. At higher frequencies additional 90[degrees] domain walls are being nucleated and propagate. Beyond 0.5 MHz, the magnetization reversal becomes progressively suppressed and finally comes to a stop at about 1 MHz.