The GMR multilayers require a large applied field to saturate and overcome the AFM coupling of the magnetic layer to display the large GMR ratios. Interestingly, Parkin et al found that the strength of the AFM coupling is a periodic function of the NM spacer [2]. Comparison with the AMR ratio of NiFe, the field sensitivity of the GMR multilayers is considerably lower, because of the large saturation fields in the multilayers. Nevertheless, we shall focus on understanding the physical origin of the GMR and understanding the GMR using simple resister network model.

Figure 25.2: (a) Current perpendicular to plane (CPP) and (b) current in plane (CIP) GMR geometries.

(a)	(b)
Figure 25.3: Resistor model of GMR.