CURRENT-PERPENDICULAR AND CURRENT-PARALLEL GIANT MAGNETORESISTANCES IN CO AG MULTILAYERS/

We report results of measurements of the perpendicular [current perpen dicular to the layer planes (CPP)] and parallel [current in the layer planes (CIP)] magnetoresistances (MRs) of Co/Ag multilayers having Co and Ag thicknesses t(Co) and t(Ag) ranging from 1.5 to 60 nm. (1) We f ind the variations of the CPP- and CIP-MRs with t(Ag) and t(Co) to be qualitatively similar to each other, suggesting that the parameters de termining both may also be similar. (2) In accord with predictions tha t CPP-MR>CIP-MR, we find their ratio pi=CPP-MR/CIP-MR to range from ab out 3 to at least 6. (3) We analyze current perpendicular to the layer plane (CPP) specific resistances, Ar-t, of Co/Ag multilayers having a wide range of Co and Ag thicknesses t(Co) and t(Ag) in terms of a two -current, series resistor model based upon the assumption that the spi n-diffusion lengths in the Co and Ag are much longer than t(Co) and t( Ag), respectively. We show first that a six parameter fit gives rather good agreement with four data sets, with the three parameters that ca n be separately checked agreeing within experimental uncertainties wit h independent measurements of the same quantities. We then examine the ability of these fits to predict the behavior of additional sets of d ata. Here we find some agreements and some disagreements. Possible rea sons for the disagreements are examined.