How predictable is the current perpendicular to plane magnetoresistance? (invited)

Prior measurements of the current perpendicular to the layer planes (CPP) resistances, taken on Co/Cu/Py/Cu (Py=Ni84Fe16) multilayers with a single pair of Co and Py thicknesses, are extended to three additional pairs of thicknesses. The same parameters, obtained from independent measurements on Co/Cu and Py/Cu multilayers that fit the original pair reasonably well, fit the three new pairs almost as well, from which we conclude that there is substantial predictability in the CPP magnetoresistance (MR). Because the predictability is not perfect, we examine the extent to which we can improve the fits to the Co/Cu/Py/Cu data by varying the Py/Cu and Co/Cu parameters within their uncertainties, without substantially weakening the fits to the original Co/Cu and Py/Cu data. We conclude by presenting the first CPP-MR measurements on Co/Ag/Py/Ag multilayers. The data are similar to those for Co/Cu/Py/Cu multilayers, but the Co/Ag/Py/Ag MRs are noticeably larger.