Ac susceptibility and magnetic interaction in Mg–Ni–Fe–O system

Abstract

A series of Mg 1− x Ni x Fe 2O 4 spinel ferrites with x=0, 0.25, 0.50, 0.75 and 1.0 have been prepared using standard ceramic method. Lande- g factor ( g), effective magnetic moments ( P eff), Curie temperature ( T c), paramagnetic Curie temperature ( θ(K)) and exchange integral ( J/ k) were calculated from ac susceptibility measurements using mutual inductance technique. With the addition of Ni ions g-values, P eff and θ(K) show increasing trend up to x=0.75 while T c continues to decrease. For x>0.75 decreasing trend in magnetic moments (n B) and θ(K) is exhibited, which could be correlated to the redistribution of cations on A and B sites. The dominant interaction in all the samples is A–B interaction, which is due to the negative values of θ(K), showing the magnetic ordering is antiferromagnetic. The Y–K angle increases gradually with increasing Ni contents and extrapolates to 60° for NiFe 2O 4. From the computation of Y–K angles for Mg 1− x Ni x Fe 2O 4, it can be concluded that mixed nickel ferrites exhibit a non-colinearity of the Y–K type while MgFe 2O 4 show a Neel type of ordering.