Preparation and Characterization of Nano Ferrites

Nickel ferrite $(NiFe_2O_4)$ and manganese ferrite $(MnFe_2O_4)$ have been prepared by a soft mechanochemical route from mixture of (1) $Ni(OH)_2$ and $α-Fe_2O_3$ and (2) $Mn(OH)_2$ and $α-Fe_2O_3$ powders in a planetary ball mill. The mixture was activated for varying duration. Soft mechanochemical reaction leading to formation of the $NiFe_2O_4$ and $MnFe_2O_4$ spinel phases were followed by X-ray diffraction, Raman and infrared spectroscopy, scanning and transmission microscopy. The spinel phase formation was first observed after 4 h of milling (case 1) and after 3 h (case 2) and its formation was completed after 25 h in both cases. The synthesized $NiFe_2O_4$ and $MnFe_2O_4$ ferrites have a nanocrystalline structure with a crystallite size of about 30 and 40 nm for cases (1) and (2), respectively. There are five Raman and four IR active modes. In order to understand better the whole process of phase formation, the Mössbauer measurements were done.