Localized canting effect in Zn-substituted Ni ferrites

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 Zn2+ ions in sublattice A. The cases where: (i) only Fe3+ ions are found in B'. and (ii) B' is occupied by Fr3+ + and Ni2+ ions are considered. The two-sublattice model with canting in sublattice B is presented for comparison with cases (i) and (ii). The canting angle 0(L), is calculated from energetic considerations, assuming that the J(1f) ion-to-ion interaction energies are not modified by the substitution of Zn2+ 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 an needed for this system, as lithium acts as a non-magnetic dilution in the octahedral sublattice. (C) 2000 Elsevier Science B.V. All rights reserved.