Sensitive and quick response micro magnetic sensor utilizing magneto-impedance in Co-rich amorphous wires

New high performance micro magnetic heads and sensors are presented utilizing the giant magneto-impedance (GMI) in the Co-rich amorphous wire. Typical performances or advantageous features of the head and sensor-are as follows; (i) head size can be reduced to about 1 mm maintaining a flux detection sensitivity of about 10/sup -5/ Oe, (ii) a rapid response with the cut-off frequency of 20/spl sim/30 MHz using a wire current of 200/spl sim/300 MHz, (iii) high temperature stability of about 0.01 %FSspl deg/C with a maximum operating temperature of about 180/spl deg/C using a negative feedback loop in the sensor circuit, and (iv) small power consumption of less than 10 mW using a self-oscillation circuit, in which a MI element voltage decreases to zero (100% change) with an external field of about 2 Oe. The basic properties and mechanism of the GMI, the head construction, the sensor construction principle, sensor circuits and sensing applications are discussed.<>