Low-frequency dynamic response and hysteresis in magnetic superlattices

We study theoretically the low-frequency dynamic response of magnetic superlattices. We have the Fe/Cr(211) structure in mind, which has been demonstrated to have a surface or bulk spin-flop phase, depending on the number of magnetic layers. We proceed by integrating the equations of motion of the coupled magnetic films in time, for an extended period. We include Landau-Lifshitz damping in the equations of motion, and drive the structure with an appropriate low-frequency held. The externally applied (nominal) de magnetic field is increased slowly. We can follow the structure through the sequence of magnetic-field-induced phase transitions. By this means, we obtain the magnetic phase diagram, chi(1) and chi(2), along with hysteresis curves in a single calculation. We also provide data on the magnetic-field dependence of the low-field susceptibility, which is in good accord with theory.