Observation of Dynamic Domain Structure in 4%Si‐Fe Single Crystals with the (110) [001] and (100) [001] Orientations Under AC Field Excitation

Abstract

The stroboscopic observation of dynamic domain structure in two types of 4%Si‐Fe single crystal with the (110) [001] and (100) [001] orientations has been made under ac field excitation, using the Kerr magneto‐optic effect. The changes of the magnetization at the surface and of the flux in the volume were measured simultaneously using a photomultiplier and a search coil wound around the specimen. The variation of the number of 180° domain walls was investigated over the wide frequency range 10–400 Hz at various flux densities. By plotting the degree of magnetic saturation at the surface against the degree of saturation in the volume, the amount of domain wall bowing was estimated in each specimen. The experimental results indicated that the wall bowing occurs even below 10 Hz and can be a main cause of the nonlinear relation of the iron loss per cycle to the frequency in the low frequency range. It was also shown that the dynamic wall profile is strongly affected by the direction of the crystallographic axis to the surface.