INFLUENCE OF ERBIUM DOPING ON VELOCITY OF MAGNETIC DOMAIN-WALL PROPAGATION IN YTTRIUM IRON GARNET

We discuss the additional damping to which magnetic domain wall motion is subject due to the replacement of a small proportion of the yttrium in yttrium iron garnet by erbium. Published ferromagnetic resonance data for a specimen of composition Er0·078Y2·922Fe 5O12 are used to predict the wall mobility in this material assuming that the erbium doping, acting according to the longitudinal relaxation model, is the sole cause of damping. Measurements are reported of the time taken to reverse the flux in single crystal toroids of pure yttrium iron garnet and of the above composition when reversal takes place by domain wall motion, following the sudden application of a magnetic field. Comparison of theory and experiment shows that the proposed mechanism controls the reversal time for the doped material between 3°K and 60°K, where the predicted damping is strong. At higher and lower temperatures the controlling mechanism, which appears to be the same in the doped and pure samples, is different and not understood.