MAGNETORESISTIVE THICK-FILM SENSOR FOR LINEAR DISPLACEMENTS

A new thick film material has been developed starting from Ni and Co powders in the ratio Ni:Co=3:1. The thermal treatment (in N,, up to 950 degrees C) of the metal films deposited on glazed alumina enables the in situ formation of the NiCo alloy. The films as created exhibit a high longitudinal (current I parallel to the field B) magnetoresistive response with Delta R/R approximate to 4% at 1.2 kGauss, and a negligible transverse one. The temperature coefficient of resistance (TCR) is approximate to 2700 ppm degrees C-1. These properties make the new material superior, from the point of view of magnetoresistive applications, to the Ni-based currently available thick film conductors. Contactless sensors for linear displacements have been created with the sensor's structure enclosing either Ni-based and Ni/Co-based meanders, having two magnetoresistive elements on each side of the substrate. This paper compares the magnetoresistive and thermoresistive properties of Ni and Ni/Co-based layers as well as the performances of the sensors in the range -20 to 120 degrees C.