Analysis of magnetic behavior of exchange-enhanced SmFeCo magnets

A series of densified exchange-enhanced SmFeCo magnets was produced by mechanical alloying, followed by a heat treatment. The nanocrystalline phases and the grain size distribution of the samples were characterized from x-ray diffraction patterns. Magnetic measurements in terms of different models were analyzed for the temperature behavior of the magnetization and coercivity. One analytical formulation was derived from the random anisotropy model predicting that with increasing M-r/M-s ratio a decreasing coercivity occurs. Another numerical approach, which is based on a micromagnetic calculation using finite element techniques was also applied. Attempts were made to improve the existing model derived from the finite element technique. The nucleation model was found to be unsatisfactory for describing the temperature-dependent coercivity. (C) 1998 American Institute of Physics. [S0021-8979(98)43011-1].