Dependence of energy dissipation on annealing temperature of melt-spun NdFeB permanent magnet materials

A model of magnetic hysteresis which was developed originally for soft magnetic materials has been applied to melt-spun ribbons of Nd2Fe14B-based material. The crucial ideas in the model description of hysteresis center on a dissipation of energy due to hysteresis which is proportional to the change in magnetization. The Nd2Fe14B material was melt-spun amorphous and then annealed for a period of 24 h at temperatures ranging from 700 to 950 degrees C. This resulted in different grain sizes, depending on annealing temperature. Consequently the hysteresis curves represent the properties of the material as a function of both annealing temperature and grain size. It was found that the magnetic properties varied systematically with annealing temperature, and hence grain size, as would be expected. When modeling the magnetic properties it was found that the model parameters also varied systematically, in particular, the energy dissipation parameter k was to a first approximation a simple linear function of the annealing temperature and decreased with increasing annealing temperature as a result of grain growth. Therefore, this study revealed a basic relationship between materials processing conditions, microstructure, model parameters, and magnetic properties. (C) 1996 American Institute of Physics.