Nanocrystalline cubic CuFe2O4: size dependent transition from ferrimagnetic to superparamagnetic behaviour

Nanocrystalline cubic CuFe2O4 have been prepared by co-precipitation method. The experimental conditions have been controlled to produce CuFe2O4 with particle size 18 nm, 7.2 nm, and 3.2 nm as calculated by Scherrer formula. Room temperature Mössbauer spectra show that 18 nm and 7.2 nm CuFe2O4 exhibit ferrimagnetism while 3.2 nm CuFe2O4 exhibits superparamagnetism. The cationic distribution calculated using Mössbauer spectra confirm to the cubic structure confirming the findings of XRD study. XPS data corroborates the finding. Low temperature Mössbauer measurements on 3.2 nm particles show gradual transformation to ferrimagnetic state.