Thermal sprayed thick-film anisotropic magnetoresistive sensors

Ni/sub 80/Fe/sub 20/ and Ni/sub 80/Co/sub 20/ alloys anisotropic magneto-resistive sensor films were deposited by plasma spray. The resistivity (/spl rho/) of the films is determined to be 40-70 /spl mu//spl Omega//spl middot/cm in the as-sprayed state. The oxygen impurity dissolved in the metal acts as a strong scattering center and results in higher resistivity. The /spl rho/ of sensor film improves significantly with thermal annealing up to 500/spl deg/C and it remains constant for further increase in temperature. The dissolved oxygen precipitates out as oxide phase during heat treatment and that reduces the scattering. The /spl rho/ values are 19 and 22 /spl mu//spl Omega//spl middot/cm for permalloy and NiCo alloy films, respectively, which are close to bulk values. The anisotropic magnetoresistance (AMR) effect is found to be increased by a factor of 2 in both the permalloy and the NiCo sensors. The /spl Delta/R/R values are increased from 2.0% to 4.0% and 2.6% to 5.8%, respectively, for permalloy and NiCo sensors.