Grain growth kinetics and magnetic properties of NiZn ferrite thin films

摘要

This paper focuses on the grain growth kinetics described by tradition phenomenological rate equation through nonlinear fitting of grain sizes for Ni_(0.5)Zn_(0.5)Fe_2O_4 ferrite thin films. The grain growth exponent n, which matches with normal grain growth, equals to 2.43 at 600 °C, and the process is controlled by anomalous solute drag which effects on the grain boundary mobility. As the annealing temperature rises from 700 °C to 900 °C, correspondingly the n goes up from 3 to 4, indicating that volume diffusion happens. The activation energy for grain growth are 22.75, 42.52, 56.32 and 85.54 kJ/mol from 600 °C to 900 °C, respectively, they are much smaller than that of the NiZn ferrite bulk. The effects of annealing temperature on the magnetic properties, phase structure and microstructure are investigated. The coercivity of NiZn ferrite thin films is mainly discussed via stress model.