MAGNETIC-PROPERTIES OF COFE2O4 POWDERS AND THIN-FILMS GROWN BY A SOL-GEL METHOD

Ultra-fine CoFe2O4 particles and thin films were fabricated by a sol-g el method and their magnetic and structural properties were investigat ed. Co-ferrite powders fired at and above 450 degrees C had only a sin gle phase spinel structure and became ferrimagnetic. Powders annealed at 200 degrees C and 350 degrees C had a typical spinel structure, how ever, they showed a transition from the paramagnetic to ferrimagnetic state as the measuring temperature decreased from the room to liquid n itrogen temperature. Co-ferrite films annealed at 650 degrees C had a single phase spinel structure without any preferred crystallite orient ation and the in-plane and perpendicular coercivity. The maximum value of the coercivity was 2550 Oe for the thin film fired at 850 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved.