XRD and Mössbauer spectroscopy investigation of Mn substituted CuFe2O4 nanoparticles

The effect of Mn substitution in Cu ferrite may present a challenge, as there are three transition metals ions distributed among the two available crystallographic sub lattices. This system also presents complicated super exchange interactions. In this study a series of five powdered samples with composition Cu(1-x)Mn(x)Fe2O4 were investigated using XRD and transmission Mössbauer spectroscopy. The variation of lattice parameter, crystallite size, and Mössbauer parameters of the product formed with the variation in the concentration of Mn has been studied. XRD study revealed the formation of pure phase spinels with FCC cubic structure having particle size ranging from 7.2 nm to 20 nm. Lattice constant value showed constant increase with increasing Mn concentration. AFM image confirms the formation of spherical shaped nanoparticles. Mössbauer spectroscopy proves to be an excellent tool for probing the local environment of Fe atoms present in such materials. Results show two sets of six finger patterns for all the samples with two double line pattern obtained for the composition with x = 0.75 and 1.0, indicating the presence of Fe in both A and B site. Increase in Mn concentration first increases the hyperfine field and then it gradually decreases. This effect is observed at both the sites. This effect is due to the relative strengths of Fe-O-X super exchange (X = Fe, Mn, Cu) as well as number of different nearest neighbour of A and B sites. The unexpected behaviour for the last two compositions can be explained by the presence of particle size distribution that results in superparamagnetic behaviour.