Mössbauer spectra and crystallite size related magnetic/electric properties of Yb substituted Zn-ferrite nanoparticles

Abstract

Copyright © 2014 American Scientific Publishers. All rights reserved. Influence of thermal-annealing-controlled crystallite size on the magnetic/electric properties of Yb substituted Zn-ferrite nanoparticles (ZnFe1.95Yb0.05O4) is studied, and results of the analysis are presented here. Room temperature Mössbauer spectrum of as-prepared sample shows coexistence of the sextet/doublet structure due to the particle size distribution. The central doublet originating from superparamagnetic relaxations of smaller particles is found to constitute the major fraction of the 57Fe signal in samples obtained by thermal annealing of as-prepared sample at various temperatures in 300 °C-800 °C range. The determined quadrupole splitting (QS) parameters are significantly higher compared to corresponding bulk counterpart value and display decreasing trend with the crystallite size increase. The ∼29 nm-sample, obtained by annealing at 800 °C, shows bulk-like properties, both in terms of the observed QS value and observed distribution of iron ions within the spinel lattice. Electric resistivity has non-monotonic dependence on crystallite-size, which could be attributed to enhanced disorder in as-prepared material. Partial substitution of iron by ytterbium in Zn-ferrite is found to increase the dielectric constant.