Coercivity vanishing induced by soft imperfections in hard magnetic materials

Coercivity of hard magnetic material with soft imperfection was studied via micromagnetic simulations established on one-dimensional scheme. A transition region of anisotropy energy between soft and hard phases was involved by considering a power function of [Formula: see text] with [Formula: see text] varied from 0.5 to 3.0. Unlike the sharp-interface connection where a lower bound of coercivity exists, the presence of [Formula: see text] transition led the coercivity reduction unbounded. The quadratic case ([Formula: see text]) showed the steepest drop of coercivity when transition region is considerably thick, following a simple inverse law as [Formula: see text] with [Formula: see text] the coercivity normalized by anisotropy field and [Formula: see text] the transition thickness normalized by Bloch length. The magnetic reversals and the behaviours of thermal agitation were explored for various [Formula: see text] cases, and correlated to the energy profiles investigated by calculation of minimum energy paths.