Exchange biased spin valve-based gating flux sensor

A hybrid type of magnetic sensor, combining the advantages of both fluxgate sensors and giant magnetoresistance sensors (GMR), was developed in this work by applying the fluxgate principle into the GMR sensors. The well-known measuring principle of the fluxgate sensor is based on the offset of the hysteresis curve and the second harmonic characteristic using the phase sensitive detection technique. The GMR spin valve was used as the soft magnetic core and the pickup coil of the fluxgate. Based on the harmonic analysis using Fourier series, the second harmonic component of the hybrid GMR-fluxgate sensor output was found to be dominated. The sensitivity of the device was maximized by turning the amplitude and the phase of the sinusoidal excitation current. The obtained sensitivity was 1.52 mV/mT and the field noise was found to be 5.7 nT/√Hz@1Hz. The non-hysteresis of the transfer V-B curve was achieved, and the nonlinearity was about 2.5% within the operation range of ±0.2 mT. The proposed sensor is an appropriate design for low field measurements and geomagnetic applications.