Magnetization and Mossbauer study of nanosize ZnFe2O4 particles synthesized by using a microemulsion method

Abstract

Nanosize ZnFe2O4 particles prepared by using a microemulsion method have been investigated by X-ray diffractometry, transmission electron microscopy, SQUID magnetometry and Mossbauer spectroscopy. All the peaks of the X-ray diffraction patterns can be attributed to a cubic spinel structure with the lattice constant alpha(o) = 8.43Angstrom. The average size of the particles, as determined by transmission electron microscopy, is 8.8 nm. A value of 54 emu/g is obtained for the saturation magnetization from 5 K results by fitting the high field data to the function sigma = sigma(s) (1 - alpha/H). Asymmetric broadening of the Mossbauer spectral lines and the large linewidths are observed and can be explained as originating from different temperature dependences on the basis of the magnetic hyperfine fields due to the distribution of Fe+3 ions at both tetrahedral and octahedral sites. The superparamagnetic behavior is also confirmed.