Localized canting effect in Zn-substituted Ni ferrites

Abstract

A model of three sublattices (A, B and B′) to describe the magnetic behavior of mixed Ni–Zn ferrites is presented. It is proposed that only sublattice B′ is affected by canting, due to the substitution of Zn 2+ ions in sublattice A. The cases where: (i) only Fe 3+ ions are found in B′, and (ii) B′ is occupied by Fe 3+ and Ni 2+ ions are considered. The two-sublattice model with canting in sublattice B is presented for comparison with cases (i) and (ii). The canting angle θ L is calculated from energetic considerations, assuming that the J ij ion-to-ion interaction energies are not modified by the substitution of Zn 2+ ions in sublattice A. The number of Bohr magnetons per molecule, n B, and the Curie temperature, T c, are predicted as a function of Zn content, z. The experimental values of n B as well as the results for T c are satisfactorily reproduced by the model described in (i). Results on Zn-substituted Li ferrite are also mentioned. It is found that additional considerations on the interactions are needed for this system, as lithium acts as a non-magnetic dilution in the octahedral sublattice.