Structure and cation distribution in superparamagnetic NiCrFeO4 nanoparticles using Mössbauer study

The structure and cation distribution in nanoparticles of chromium doped nickel-ferrite synthesized using the solution self-combustion technique has been studied using Mössbauer spectroscopy. Powder XRD analysis of samples confirmed the formation of single-phase pure NiCrFeO4 nanoparticles. The structural parameters were investigated by powder X-ray diffraction followed by Rietveld refinement using the FullProf method. The crystallite size obtained from XRD matches well with the particle size seen in TEM. From the room-temperature Mössbauer study, NiCrFeO₄ nanoparticles are found to exhibit superparamagnetism. The low-temperature Mössbauer studies indicate superexchange interaction between A and B sites, novel cation distribution, (Fe_0.2Ni_0.8)^A [CrNi_0.2Fe_0.8]^B with an unusual presence of Ni²⁺ at A site and spin canting effects.