Mössbauer spectroscopic analyses of Mg0.9Cu0.1Mn0.05CrxFe1.95−xO4 spinel ferrites

The effect of the substitution of paramagnetic trivalent chromium ions in non-stoichiometric magnesium–copper–manganese ferrites has been studied with the composition, Mg0.9Cu0.1Mn0.05CrxFe1.95−xO4 with x varying from 0.0, 0.1 to 0.9 in steps of 0.2 wherein a small amount of Cu2+ ions have been added to prepare the series at lower sintering temperature. The single-phase spinel structure of these samples has been confirmed from X-ray diffraction analyses. Mössbauer spectra of these samples studied at room temperature(300 K) showed two characteristic ferrimagnetic Zeeman sextets for lower concentration of Cr3+ followed by relaxation phenomenon and the spectrum collapses to a paramagnetic doublet for x = 0.9. The dependence of Mössbauer parameters, viz, isomer shift, quadrupole splitting and hyperfine magnetic field on Cr3+ concentration have been discussed. The variation of hyperfine magnetic field with increasing Cr3+ content has been explained on the basis of Neel's molecular field model.