Linearized giant-magnetoresistance sensor for static field measurement

The giant-magnetoresistance (GMR) magnetometer for measuring the dc magnetic field is investigated in this work. By using a sinusoidal excitation, the hysteresis of the sensor can be substantially reduced. By extracting the Fourier components of the time trace of voltage output, it is found that the typical output voltage is the combination of odd harmonics of the excitation frequency. By detecting the multi-harmonic response with an ac driving circuit, the hysteresis and the nonlinearity is reduced. The improved sensor is suitable for sensing the dc fields in the micro-tesla range.