The effect of particle size on structural and magnetic properties of Zn0.5Co0.5Fe2O4 prepared by glycol-thermal technique

Abstract

Zn0.5Co0.5Fe2O4 fine particles with grain size of about 9 mm were synthesized using the glycol-thermal method. Grain size increased to about 22 mm after annealing from 400 °C to 1100 °C. The X-ray diffraction (XRD) analysis confirmed formation of a single phase cubic structure of the compounds investigated. TEM images revealed agglomerated particles with spherical shapes and confirm particles sizes indicated by XRD data. Mössbauer spectra showed broad spectra due to fine particles which indicate ferrimagnetic ordered spin state. A general increase in hyperfine fields after annealing at temperatures above 500 °C due to increasing particle size relates well with saturation magnetization which increased to about 75 em/g after annealing at 1100 °C. The almost zero coercive fields at about 300 K and “S” shaped magnetization curves relating well with the “hump” in ZFC curve reveal superparamagnetic fine particles. An increase from about 0.1 kOe at room temperature to 3 kOe at 10 K due to spin freezing has been observed.