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 of 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(-5) Oe, (ii) a rapid response with the cut-off frequency of 20 approximately 30 MHz using a wire current of 200 approximately 300 MHz, (iii) high temperature stability of about 0.01 %FS/-degrees-C with a maximum operating temperature of about 180-degrees-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.