Mossbauer studies of Cr substituted bulk and nano Co-Zn ferrites

X-ray and Mossbauer studies have been carried out for bulk and nano sized CrxCo(0.5-x)Zn0.5Fe2O4 (X = 0, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5) prepared through wet chemical co-precipitation method. The hyperfine fields in the bulk samples at tetrahedral A site is independent of the substitution while it decreases sharply at octahedral B site due to the quenching of A-B super-exchange interaction due to the addition of Cr ions which preferentially occupy the octahedral B sites. The average particle size for the nano samples was seen to decrease exponentially with the addition of Cr. The RT Mossbauer spectra for all the nano samples show only two paramagnetic doublets showing the superparamagnetic relaxation phenomena in these samples due to small particle sizes involved.