Anomalous variation of coercivity with annealing in nanocrystalline NiZn ferrite films

The sputter deposited NiZn ferrite thin films were studied as a function of annealing temperature. The magnetization showed a monotonic increase with increasing annealing temperature. The coercivity shows a minimum at annealing temperature of 400 degreesC and shows a value of 14 Oe. Transmission electron microscopy study indicated that the grain size increases from similar to3 nm for the as-deposited case to similar to15 nm for the film annealed at 800 degreesC. The observed coercivity behavior could be attributed to the defects present in the films, the change in cation distribution, and the grain growth. (C) 2002 American Institute of Physics