Cation distribution dependence of magnetic properties of sol-gel prepared MnFe2O4 spinel ferrite nanoparticles

MnFe2O4 nanoparticles have been synthesized with a sol-gel method. Both differential thermal and thermo-gravimetric analyses indicate that MnFe2O4 nanoparticles form at 400 oC. Samples treated at 450 and 500 oC exhibit superparamagnetism at room temperature as implied from vibrating sample magnetometry. Moessbauer results indicate that as Mn2+ ions enter into the octahedral sites, Fe3+ ions transfer from octahedral to tetrahedral sites. When the calcination temperature increases from 450 to 700 oC, the occupation ratio of Fe3+ ions at the octahedral sites decreases from 43% to 39%. Susceptibility measurements versus magnetic field are reported for various temperatures (from 450 to 700 oC) and interpreted within the Stoner-Wohlfarth model.