TERNARY NIFEX AS SOFT BIASING FILM IN A MAGNETORESISTIVE SENSOR

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) trilayer sensor. 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 rho. 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)rho that takes into account both the rate of increase in B(s) and the rate of decrease in rho 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.