Abstract
This paper presents a simple scheme for enhancing the resolution of giant magnetoresistance (GMR) sensors by making use of an AC-biased method. In doing so, an alternating voltage was used to power the GMR sensor. As in the case of high-frequency bias, significant suppression of low-frequency (1/f) noise was experimentally observed. With the bare GMR sensor, the 1/f noise value at 1 Hz was recorded to be 15 nT/√Hz, whereas applying the AC bias, the noise was reduced significantly by a factor of 30, with a minimum noise level of 0.5 nT/√Hz@1 Hz. Furthermore, the hysteresis (Hc) of the sensor was also collapsed from 0.1 to 0.015 mT with a negligible offset. The performance of the AC-biased scheme was verified by measuring the Earth’s magnetic field with the measured error being minimized from 2.5 μT down to 0.4 μT. The favorable results indicate that the proposed scheme is a pertinent way to improve the resolution of pinning GMR sensors in ultra-weak magnetic fields and static magnetic field measurements.
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