Effect of domain transformation on the magnetic properties of CuxNi1−xFe2O4 ferrites

We report the effect of crossover from multi- to single-domain particles on the magnetic properties of CuxNi1−xFe2O4 (x=0 and 0.5) oxides due to grain size reduction to nanometer scale. The Mössbauer spectra for milled nanosized powder show a combination of ordered and super-paramagnetic behavior. The coercive field (HC) is found to increase with reduction in grain size (G) according to the equation HC=am+bm/G for multi-domain particles. For single-domain particles HC decreases with G according to HC=as−bs/G2.