Giant Magneto-Impedance Thin Film Magnetic Sensor

A thin film sensor for sensing magnetic fields bellow 10 Gausses is designed and fabricated based on a giant magneto-impedance (GMI) structure. Analytical equations describing GMI effect have been employed to design the sensor over the designated magnetic field and signal frequency. The GMI multilayer is comprised of an Au layer (200 nm) sandwiched between two Co₇₃Si₁₂B₁₅ magnetic layers (400 nm). Various structures with different shapes and ratios have been studied to achieve the optimum performance. The sensors are fabricated on a glass wafer employing thin-film micro-fabrication processes. The paper also presents a new post-processing step to magnetize the GMI multilayer. The impedance of the GMI sensors as a function of external magnetic and excitation frequency is reported and discussed. The sensor has been utilized to change the state of an On/Off circuit in the presence/absence of magnetic field.