Observation of Static Domain Structures of Thin-Film Magnetoimpedance Elements With DC Bias Current

We investigate changes in domain structures of thin-film magnetoimpedance elements with the easy-axis angles in the range of 0°-30° upon the application of dc bias current directly to the elements as well as the dc external magnetic field. All of the elements 180° domains at zero field when the bias current is zero. The angle of 180° domains depends on the direction of the easy axis. The changes in a domain configuration due to the bias dc current do not have a systematic behavior; instead, complex variations are observed. However, the field range at which multi-domain structures appear tends to be narrower with the increase in the absolute dc bias current value. The complex changes depend on the complex field distribution based on the applied dc external field and bias field generated by the dc current. The impedance does not exhibit significant changes around fields where changes in domain configuration occur, which implies that the magnetization rotation is the dominant factor for the impedance changes at high frequencies.