Characterizing interactions in exchange-spring magnets using a mean field Stoner-Wolhfarth model

Pr8Fe88B4 ribbons prepared by melt spinning and subsequent annealing have been investigated by x-ray diffraction, thermomagnetic analysis, an atomic force microscope and a superconducting quantum interference device magnetometer. The results show that the annealed ribbons consist of the Pr2Fe14B and alpha -Fe phases. The mean grain size of the samples increases with the annealing temperature and the annealing time. The result of magnetic measurement shows that the exchange interaction between the hard and soft phases in the sample with a smaller mean grain size is larger than that in the sample with a larger mean grain size. The particle exchange interaction in Pr8Fe88B4 nanocomposite magnets was calculated using the mean field Stoner-Wohlfarth model. We found that the result calculated from mean field Stoner-Wohlfarth model is in agreement with the conclusion gained from microstructure observation and magnetic measurement.