Mössbauer study on the magnetic properties and cation distribution of CoFe2O4 nanoparticles synthesized by hydrothermal method

The structural, morphological, magnetic properties, and cation distribution of CoFe2O4 nanoparticles were investigated by X-ray diffraction, transmission electron microscopy, Mossbauer spectroscopy, and vibrating sample magnetometer at room temperature. Single-phase CoFe2O4 nanoparticles were synthesized by hydrothermal method. The results indicated that the average crystallite size and the magnetic hyperfine field of CoFe2O4 nanoparticles increased with increasing reaction time, which suggested the improved crystallinity and magnetic order. The relative absorption area of component B in Mossbauer spectra assigned to the Fe3+ ions occupying the octahedral B sites decreased with increasing reaction time, indicating that more Co2+ ions migrated from the tetrahedral A sites to the B sites. The saturation magnetization of the samples increased with increasing reaction time, which resulted from the increase in crystallite size with longer reaction time. The increase of coercivity was attributed to both increasing crystallite size and more Co2+ ions migrating to the B sites with increasing reaction time.