Specimen shape influence on hysteretic response of bulk ferromagnets

Influence of shape of a specimen is questioned by computational modeling. A new mesoscopical-level model modifying the conventional micromagnetics in a suitable way is used. Numerical simulations made for uniaxial ferromagnets as, e.g., CoZrDy demonstrate explicit dependence of the hysteretic response on the geometry of the specimen. In particular, it is shown how non-ellipsoidal shape of the specimen causes the main hysteresis loop to be round. Minor loops occur only if there is more than one activation threshold (i.e. one coercive force). One option is to include spatial fluctuations in the coercive force, which is demonstrated computationally, as well.