DOMAIN SIZE AND SPIN-WAVES IN A REENTRANT SPIN-GLASS

Neutron depolarization measurements on the amorphous alloys, (Fe xNi1-x) 75P16B6Al 3, above the multicritical concentration x>0.15, indicate that low-field domain sizes are in the range of 2-4 μm. This is approximately two orders of magnitude larger than the length scales observed with magnetic small-angle neutron-scattering techniques. The depolarization shows evidence of domain size changes and/or canting as the reentrant-spin-glass state is entered, in agreement with the small-angle scattering results. Sufficiently near to the multicritical concentration the results cannot be interpreted solely in terms of a canting transition, because the change in depolarization is too great. In the samples where anomalous low-temperature spin waves have been observed, the depolarization behaves as in a conventional ferromagnet, indicating that the reentrant-spin-glass spin-wave behavior is related to a canting transition. The spin-wave spectrum calculated for a model canting system reasonably explains the observed spin-wave measurements.