Dipolar interactions in magnetisation reversal of R2Fe14B hard materials

Abstract Two main experimental parameters denoted, respectively, by α (or α K ) and N eff , are usually deduced from the comparison between experimental and calculated temperature dependence of the coercive field, μ 0 H c , in hard magnets. The parameter N eff , is found to be model dependent. This implies that it is not only representative of dipolar interactions as it should. In the present paper, it is shown that the differences in N eff from one sample to another are not model dependent to the same extent. It is suggested that these differences represent first order differences in inter-particle dipolar fields. In a dense magnet, the strength of this field is estimated 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-called global model (Givord et al., IEEE Trans. Magn. 24 (1998) 1921).