Ternary NiFeX as soft biasing film in a magnetoresistive sensor

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Abstract
The properties of NiFeX ternary films (X being Al,Au,Nb, Pd, Pt, Si, and Zr) have been studied for soft‐film biasing of the magnetoresistive (MR)trilayersensor. In general, the addition of the element X into the NiFe alloy film decreases the saturation magnetization B s and magnetoresistance coefficient of the film, while increasing the film’s electrical resistivity ρ. One of the desirable properties of a soft film for biasing is high sheet resistance for minimum current flow. A figure of merit B s ρ that takes into account both the rate of increase in B s and the rate of decrease in ρ when adding X element was derived to compare the effectiveness of various X elements in reducing the current shunting through the soft‐film layer. Using this criterion, NiFeNb and NiFeZr emerge as good soft‐film materials having a maximum sheet resistance relative to the MR layer. Other critical properties such as magnetoresistance coefficient, magnetostriction, coercivity, and anisotropy field were also examined and are discussed in this paper.