Mossbauer, X-ray diffraction and AC susceptibility studies on nanoparticles of zinc substituted magnesium ferrite

Nanoparticles of zinc substituted Mg-ferrite with compositions Mg((1-x))ZnxFe2O4 (x=0.15, 0.30 and 0.50) having particle sizes in the range 6.4 nm to 21.4 nm prepared by the co-precipitation method were characterized by Fe-57 Mossbauer spectroscopy, X-ray diffratometry and AC magnetic susceptibility measurements. Mossbauer measurements at room temperature and down to 20 K clearly indicate presence of superparamagnetic particles in all the samples. AC magnetic susceptibility data show lowering of blocking temperature with decrease of particle size. Superparamagnetic relaxation was observed for larger particle size in samples with higher Zn content, which is attributed to the weakening of A-B exchange interaction in ferrite lattice due to replacement of Fe3+ in tetrahedral site by Zn2+ ions.