Variation of the Magnetic Domain and GMI Property of a HFC-Type Magnetic Field Sensor with Inclined Domain Walls Resulting from the Application of an External Magnetic Field in the Measurement Direction

摘要

A change in the magnetic domain structure of a high-frequency carrier-type (HFC-type) thin-film magnetic field sensor (or giant magnetoimpedance, GMI, sensor) with inclined ladder-line magnetic domain walls was investigated as a function of an external magnetic field. The GMI property of the same sensor element was also investigated. Comparison of these data leads to the following results: The application of an external magnetic field causes a drastic change in the domain structure, from an inclined ladder-line to a single domain on a threshold magnetic field. The threshold field is different for increasing and decreasing magnetic fields. This hysteretic phenomenon is in accord with the hysteresis of the GMI property. It was investigated theoretically by using the bias susceptibility model of a single-domain magnetic thin-film with uniaxial anisotropy. This theoretical model predicts that contiguous inclined ladder-line domains on a 180 deg wall will have different values for the high-frequency permeability. An approximate estimate of the total sensor impedance obtained by adding the impedances of all the ladder-line domains shows that the hysteresis of the domain leads to the hysteresis of the GMI property. It also explains why inclined ladder-line HFC-type sensors have high sensor gain.