Study of cation distributions in spinel ferrites MxMn1-xFe2O4 (M=Zn, Mg, Al)

Powder samples of the ferrites MxMn1-xFe2O4 (M = Zn, Mg, Al) were prepared using a chemical co-precipitation method. X-ray diffraction analysis showed that the three series of samples had a single-phase cubic spinel structure and that there was a decrease in the lattice parameters with increasing x. There were different dependences on the doping level x of the magnetic moments (μexp) for the three series of samples measured at 10 K. We found a non-monotonic behavior for μexp as a function x for the Zn doped samples with a maximum at x = 0.4, while μexp decreased monotonically with increasing x for the Mg and Al doped samples. On the basis of the O2p itinerant electron model, the magnetic moment direction of the Mn3+ cations is expected to be antiparallel to those of the Mn2+ and Fe cations in these samples. With this assumption, the curves of μexp versus x for the three series of samples were fitted using a quantum-mechanical potential barrier model earlier proposed by our group, and the cation distributi...