Domain wall motion in permalloy thin film cores with toroidal and multi-aperture configuration

Domain wall motion and flux patterns in vacuum-deposited thin film cores were observed under dc and pulsed magnetic fields by using the Kerr magnetooptic effect. Two of the thin film cores have a uniaxial magnetic anisotropy around the circumference, and the other is magnetically isotropic. The domain configuration with current through the center of the hole is circular, and expands radially. Domain wall position was quantitatively measured as a function of dc and pulse current. Circular multi-domain walls like an onion slice appear by switching the polarity of the current, and are moved by the pulse field. By exciting the thin film cores with a drive winding, a notched domain appears without continuity of magnetic flux, but the thin film coated on the permalloy bulk core has a circular domain with continuity of flux. From these results, it is confirmed that the thin film has the domain configuration which depends on the distribution of applied magnetic field, and that the thin film coat transcribes the domain wall motion in the bulk core.