Reduction of the bias field of a high-frequency carrier-type (HFC-type) thin-film magnetic field sensor (or giant magnetoimpedance, GMI, sensor) was investigated on the basis of a new technique for realizing inclined ladder-line magnetic domain walls against the transverse direction of a sensor strip. A new idea for controlling the angle of a magnetic domain wall is to apply a magnetic field in a direction slightly inclined from the transverse direction of the sensor strip during magnetic field annealing, where the parameters are the aspect ratio of the sensor cross-section and the direction and strength of the annealing magnetic field. This method is effective for a small thin-film HFC-type sensor with a width of less than 50 μm and an aspect ratio of the sensor cross-section of less than 15. Increasing the angle between the domain wall and the transverse direction decreases the bias field. This reduction of the bias field more than triples the sensor gain in a frequency range up to 600 MHz. The above experimental results qualitatively agree with a calculation based on the bias susceptibility model of a single-domain magnetic thin film with uniaxial anisotropy.

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