Cation distribution and Mossbauer spectral studies of Mg0.2Mn0.5Ni0.3InxFe2-xO4 ferrites (x=0.0, 0.05 and 0.10)

The effect of substitution of diamagnetic indium ions in Mg-Mn-Ni ferrite with the composition Mg(0.2)Mn(0.5)Ni(0.3)InxFe(2-x)O(4) (x = 0.0, 0.05 and 0.10) synthesized by citrate precursor technique has been investigated. Crystallographic and magnetic properties have been investigated using X-ray diffraction, TEM, VSM and Mossbauer spectroscopy. The single phase cubic spinel structure of these samples has been confirmed from X-ray diffraction analyses. In3+ ions initially prefer tetrahedral A-site up to x = 0.05 due to which saturation magnetization and magnetic moment increases, followed by subsequent decrease when indium ions begin to occupy octahedral B-site for higher concentration of x. Magnetization measurements exhibit Neel's collinear ferrimagnetic structure for samples up to x = 0.05. Mossbauer spectra of these samples studied at 300 K show two characteristic ferrimagnetic Zeeman sextets for x = 0.0, followed by relaxation phenomenon corresponding to x = 0.05 and 0.10. Mossbauer measurements also show dependence of Zeeman spectral lines on smaller particle size which is indicative of their superparamagnetic nature. The dependence of Mossbauer parameters such as isomer shift, quadrupole splitting, linewidth and hyperfine magnetic field on In3+ ions concentration have been discussed. The variation of hyperfine magnetic field with increasing In3+ ions content has been explained by Neel's molecular field theory. (C) 2013 Elsevier B.V. All rights reserved.