Fabrication of GMR Sensors With Antiphase Magnetization Modulation and Closed-Loop Operation

Giant magnetoresistance (GMR) effect is widely used to detect a small magnetic field with high signal-to-noise (
$S/N)$
ratio, and high-quality and low-cost GMR sensors are commercially available. However, conventional GMR sensors have some drawbacks, such as low linearity due to the hysteresis of magnetic layers and a temperature drift due to the variation of the resistance with temperature. In this study, we fabricated novel GMR sensors with antiphase magnetization modulation and closed-loop current-field feedback. The antiphase modulation is effective to decrease the 1/
$f$
noise as reported by Shirotori et al. (2021), and the closed-loop operation was confirmed to improve the linearity and reduce the temperature drift of the sensor output. We obtained a low non-linearity of 0.4% as well as a low temperature drift of 0.05%/°C by using the fabricated sensor, which was smaller than those of the conventional open-loop operation, non-linearity of 1.7%, and temperature drift of 0.25%/°C.