Abstract
The dependence of the thermal remagnetization (TR) in sintered hard magnets on external magnetic fields has been investigated in order to determine more precisely the grain-interaction fields in the DC-demagnetized state. That negative external field at which the TR or its initial slope vanishes or changes its sign, corresponds well to the theoretical parameter σ f, i.e. the distribution width of internal field fluctuations. For the “normal” TR of the metallic magnets SmCo 5, Sm 2Co 17 and NdFeB these fields are of the order of −0.5, 0.25 and −0.04 T , respectively. For the “inverse” TR at the hard ferrites this external field is about −0.02 T . The systematic variation of the TR-curves with a small external field is well explained by our theoretical model and leads to a refinement of the parameters for SmCo 5 and barium ferrite. Susceptibility measurements with small alternating fields, carried out at different points of the TR curve, as well as repeating TR-experiments at SmCo 5 demonstrate clearly that the TR is mainly due to the contribution of the “weak” grains, remagnetizing in the interaction fields of the “hard” grains.
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