Dynamic magnetization process of nanocrystalline tape wound cores with transverse field-induced anisotropy

The correlation between dynamic magnetic domain formation and dynamic magnetization loss is studied in nanocrystalline FeCuNbSiB tape wound cores with different strengths of transverse field-induced anisotropy. A significant excess loss component is measured, in particular for high induction levels. The excess loss cannot be explained by homogeneous magnetization rotation, the ideal magnetization process for a transverse field-induced anisotropy. In fact, dynamic domain observation reveals inhomogeneous rotation of magnetization, wall displacement processes, and domain nucleation besides homogeneous rotation. Domain refinement is accordingly observed with increasing frequency. The domain width is smallest for cores with weak induced anisotropy, where excess loss is the lowest. In these cores, surface roughness yields residual domains, which persist at field strengths above the inductively measured saturation field.