Compensating temperature-induced sensitivity changes in thin film NiFeCo magnetoresistive magnetometers

The temperature dependence of the sensitivity and resistance of magnetoresistive thin film magnetic sensors has been investigated. Magnetoresistive sensors were fabricated from a range of zero-magnetostrictive NiFeCo alloys with cobalt contents between 0 and 25 wt.%. In the temperature range considered (0 to 60 deg.C) the sensitivity was found to fall and the resistance to rise almost linearly for all of the alloys. The response of the sensor to an externally applied field is proportional to its supply voltage. In the simple case of true complementary correspondence between the temperature coefficients of device resistance and sensitivity a constant-current drive would achieve perfect temperature compensation of sensitivity. For all alloys where the degree of divergence between the temperature-resistance and temperature-sensitivity characteristics is known, electronic control systems incorporating this relationship may be used to provide inherently accurate temperature compensation.