Magnetization loss and domain refinement in nanocrystalline tape wound cores

Stroboscopic Kerr microscopy observations of the dynamic magnetization process on nanocrystalline Fe73Cu1Nb3Si16B7 tape wound cores with different induced longitudinal anisotropy Ku are presented. As the frequency of the magnetic field increases from the quasi-static case up to 10 kHz, domain refinement is distinctive. The domain wall multiplication depends on the strength of Ku which influences excess losses. The original wide domains of the core with the weakest induced anisotropy even decay into a patchy domain pattern at 1 kHz. The occurrence of the patchy domains is discussed in terms of induction rate, amplitude, and the influence of residual anisotropies.