ORIGIN OF THE SPIN-CANTING ANOMALY IN SMALL FERRIMAGNETIC PARTICLES

The spin-canting anomaly, in which fine ferrimagnetic iron-oxide particles are not completely saturated by large magnetic fields, is usually attributed to noncollinear surface moments. Using a simple mean-field model we show that the anomaly is in fact a routine manifestation of the response of a uniaxial ferrimagnetic powder to an applied field. This view is supported by the modeling of Fe-57 Mossbauer spectra of Co-adsorbed gamma-Fe2O3 recorded at 4.2 K in applied fields of 6.0 and 7.6 T.