Thin-film magnetic sensor using high frequency magneto-impedance (HFMI) effect

Abstract

This study reports on the performance of a thin-film magnetic sensor which uses the high frequency magneto-impedance (HFMI) effect. In order to obtain a high sensitivity and a large voltage change ratio (/spl Delta/Vpp/Vpp(0): corresponds to the MR ratio), a strip pattern, a closed magnetic circuit, and a NiFe/SIO/sub 2/ multilayer film structure are adopted for the magnetic films of the sensor. A /spl Delta/Vpp/Vpp(0) of 60-70% is achieved by applying an external magnetic field of several Oe. Moreover there is no hysteresis or no Barkhausen noise in this sensor, which has a magnetic film width of 10 /spl mu/m. In terms of linearity, the sensor exhibits modulation degree (m) of 12% and a total harmonic distortion (THD) of 0.8%.< >