High coercivity in SiO2-doped CoFe2O4 powders and thin films

Mossbauer and magnetic studies have shown that 1-2 wt % of SiO2 could be di ssolved in the CoFe2O4 structure. Changes in magnetization and Curie temper ature 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 C o-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 pos sessed a coercivity of 7.4 kOe. Spring-magnet behavior was observed, indica ting the possible presence of remanence enhancement due to exchange couplin g because of nanocrystalline structure. (C) 2000 American Institute of Phys ics. [S0003-6951(00)01348-6].