Size dependent structural and magnetic behaviour of CaFe2O4

CaFe2O4 nanocrystalline powders were synthesized through sol–gel treatment in which the stoichiometric mixing of various nitrates involving calcium and iron in presence of citric acid was performed. Subsequently, the as prepared sample was annealed at various temperatures in order to obtain the fine distribution of size including the bulk counterpart. The samples were then characterized using powder X-ray diffraction followed by 57Fe Mössbauer spectroscopy, SQUID as well as vibrating sample magnetometry. The results of spectroanalyses revealed that the samples were formed in single phase cubic spinel structure and exhibits room temperature superparamagnetism, except the bulk one, which crystallizes in characteristic orthorhombic structure of CaFe2O4 and displays trivial coercivity and remanent magnetization at room temperature.

► Nanocrystalline CaFe2O4 in cubic spinel phase is synthesized using sol–gel method.
► Reported common extra phase like CaFe2O5 was not detected in our sample.
► Cubic to orthorhombic structural phase transition take place on annealing at 1000 °C.
► Nanocrystalline CaFe2O4 is superparamagnetic at room temperature.
► The saturation magnetization and blocking temperature increases with particle size.