Influence of domain walls on the singular point detection of energy losses in hard magnetic materials

The imaginary part of the second harmonic of the reversible parallel susceptibility (RPS) has been recently demonstrated to be a sensitive probe for determining the anisotropy fields in polycrystalline hard magnetic materials, by means of the singular point detection technique (SPD). A modified SPD theory is depicted here considering the presence of domain walls in the multi-domain crystallites, on the basis of Néel's phase theory. Measurements performed on Ba-ferrite random powder show that the energy losses related to domain wall motion are likely at the origin of the observed effect.