A THEORY OF WALL MOBILITY IN WEAKLY DAMPED INSULATING FERROMAGNETS

The classical calculation of the Bloch wall mobility, based on the Landau-Lifschitz-Gilbert equation, leads to a result which is 1000 times larger than the experimental value found for very pure yttrium iron garnet. The authors criticize this approach and propose a novel mechanism. It is argued that the non-zero transverse magnetization of the wall induces a magnetic back-flow around the wall, and hence a drag force proportional to the velocity. A correct order of magnitude of the mobility is obtained if one assumes that the intrinsic relaxation times of the medium are very different for high frequencies (where resonance experiments are performed) and low frequencies, relevant to the wall motion. © 1990 IOP Publishing Ltd.