Dynamic losses and domain refinement in nanocrystalline tape wound cores

Soft magnetic nanocrystalline toroidal tape wound cores of Fe₇₃Cu₁Nb₃Si₁₆B₇ with three different strengths of induced longitudinal anisotropy K_u have been studied. The power loss per cycle rises with increasing K_u. The distinctions in the power losses of the cores are due to differences in the excess eddy current losses. Wall multiplication rises with decreasing strength of K_u. An increasing number of active domains reduces the wall velocity, yielding smaller excess eddy current losses. The mean surface wall velocity approaches a limiting value with increasing frequency. This is connected to a change in the magnetization process from wall displacement to nucleation of patchy domains. The arising of patchy domains is discussed in terms of the induction rate and the influence of residual anisotropies.