Domain Structures and High-Frequency Response of Magnetization for CoNbZr Stripe Films

The domain structures and high-frequency response of the magnetization of amorphous soft magnetic CoNbZr films were studied, using the Bitter method and scanning Kerr-effect microscopy. A Lifshitz-type domain structure, characterized by wedge-shaped domains, was observed in the films (stripe-shaped, over 100 μm wide and 1 μm thick). The change in magnetization associated with 180° domain wall movement increased with increasing frequency, reaching a maximum near 5 to 10 MHz, whereas the change in magnetization at the walls of the wedge-shaped domains or at 90° domain walls was highest near 30 MHz. The loss factors due to these magnetization changes were three to six times that due to magnetization rotation at frequencies between 20 MHz and 40 MHz. These results imply that the changes in magnetization due to the wedge-shaped domain walls and 90° domain walls exert some influence on the Q factor of thin-film inductors at high frequencies above 10 MHz.