Design of 3-D Magnetic Field Sensor With Single Bridge of Spin-Valve Giant Magnetoresistance Films

A 3-D magnetic field sensor for geomagnetic field measurement was designed, fabricated, and characterized in this paper. The device comprises spin-valve giant magnetoresistance sheet films of Si-SiO₂/Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta to form a Wheatstone bridge using separate chips and a magnetic flux guide. The reduction of hysteresis and control of operation point were solved using the technique applying both the ac and dc magnetic biasing. The outputs from each axis were obtained using a computer-based driving and detection systems to retrieve the x-, y-, and z-field components. The sensitivities were found to be 0.25, 0.15, and 0.07 mV/V/Oe for x-, y-, and z-components, respectively. The proposed concept can be realized as a miniature 3-D magnetic field sensor of low cost and low power.