Role of ferric ions in the magnetic interactions of substituted iron molybdate

Abstract

The magnetic interactions in titanium and zinc substituted Fe2MoO4 has been analyzed with respect to Fe2+ and Fe3+ ion concentrations on the two sites of the spinel lattice. The concentrations of Fe2+ and Fe3+ ions on the two sites of the spinel lattice were determined from the Mössbauer spectra of the samples recorded in their paramagnetic state. Substitution of molybdenum by titanium decreases the Fe3+ ions on both the sites of the ferrite. The decrease in Fe3+ ion concentration leads to a decrease in the A–O–B and B–B interactions and thus decreases the ferrimagnetic Curie temperature (TC). Substitution of Fe2+ on the tetrahedral site (A) of Fe2MoO4 by Zn2+ leads to an increase in Fe3+ concentration on the tetrahedral site and thus the A–A and A–O–B interactions become strong which explains the absence of compensation temperature. Also, the increase in Fe3+ content on the A site of the zinc substituted samples initially leads to a relatively small decrease in TC, compared to the titanium substituted samples.