THIN-FILM MAGNETIC SENSOR USING HIGH-FREQUENCY MAGNETO-IMPEDANCE (HFMI) EFFECT

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 (Delta V pp/V pp(0) : corresponds to the MR ratio), a strip pattern, a closed magnetic circuit, and a NIFe/SIO2 multilayer film structure are adopted for the magnetic films of the sensor. A Delta V pp/V PP(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 mu m. In terms of linearity, the sensor exhibits modulation degree (m) of 12 % and a total harmonic distortion (THD) of 0.8 %.