Magnetic interactions in Cu-substituted manganese ferrites

A series of Mn1−xCuxFe2O4, with x=0, 0.25, 0.50, 0.75 and 1.0, spinel ferrites were prepared by standard ceramic method, to study the effect of compositional variation on magnetic susceptibility, saturation magnetization (Ms), Curie temperature (Tc) and magnetic moments (μB). The Curie temperatures have been evaluated by measuring the ac susceptibility using the mutual inductance technique. On increasing Cu contents from 0.0 to 0.50, the saturation magnetization increases while the Curie temperature decreases. On further increase in Cu contents, x>0.50 a decreasing trend in Ms is exhibited while Tc continues to decrease. This effect can be partially related to the low magnetic moments of Cu+2 ions. The dominant interaction in all ferrite samples is A–B interaction which is due to the negative values of the characteristic temperature θ(K) showing that the magnetic ordering is antiferromagnetic. The Y–K angle increases gradually with increasing copper contents and extrapolates to 90° for CuFe2O4. From the computation of Y–K angles for Mn1−xCuxFe2O4, it can be concluded that the mixed copper ferrites exhibit a non-collinearity of the Y–K type while MnFe2O4 shows a Neel type of ordering.