High coercivity in SiO2-doped CoFe2O4 powders and thin films

Mossbauer and magnetic studies have shown that 1-2 wt % of SiO2 could be dissolved in the CoFe2O4 structure. Changes in magnetization and Curie temperature were observed. The presence of SiO2 might enhance magnetic anisotropy. Coercivity values of up to 3.5 kOe were measured for mechanically alloyed CoFe2O4/SiO2 powders. High coercivities were also achieved in SiO2-doped Co-ferrite thin films prepared by sputtering technique. The Co-ferrite thin film deposited on a silicon wafer using a 5 wt % SiO2/Co-ferrite target possessed a coercivity of 7.4 kOe. Spring-magnet behavior was observed, indicating the possible presence of remanence enhancement due to exchange coupling because of nanocrystalline structure. (C) 2000 American Institute of Physics. [S0003-6951(00)01348-6].