Dipolar interactions in magnetisation reversal of R2Fe14B hard materials

Two main experimental parameters denoted, respectively, by alpha (or alpha (K)) and N-eff, are usually deduced from the comparison between experimenta l and calculated temperature dependence of the coercive field, mu H-0(c), i n hard magnets, The parameter N-eff, is found to be model dependent. This i mplies that it is not only representative of dipolar interactions as it sho uld. In the present paper, it is shown that the differences in N-eff from o ne sample to another are not model dependent to the same extent. It is sugg ested that these differences represent first order differences in inter-par ticle dipolar fields. In a dense magnet, the strength of this field is esti mated to be 0.4 M-s, and the total dipolar field involved in magnetisation reversal is 0.8 M-s. This value is close to the one deduced in the so-calle d global model (Givord et al., IEEE Trans. Magn. 24 (1998) 1921). (C) 2001 Elsevier Science B.V. All rights reserved.