Magnetic properties of Ni-Co thick-film magnetoresistors

Magnetic susceptibility from 300 to 900 K, room temperature hysteresis cycles and saturation magnetization were investigated in screen printed and fired NiCo-based layers prepared at various peak temperatures. A bulk NiCo metal sheet of comparable composition was also studied. Values of the magnetic polarization J of 0.28 and 0.435 T were obtained (at 200 kA/m) for films prepared at 750 and 950°C, respectively, in contrast with J=0.98 T for the bulk alloy. In addition, the magnetoresistive responses of the layers and the sheet were plotted. These data suggest that strains, pores and lack of composition homogeneity in the films concur in affecting their magnetic properties, and are responsible for their reduced magnetoresistance anisotropy (e.g. ca. 4% for films as compared to ca. 8% for the bulk alloy at H=80 kA/m).