Perpendicular giant magnetoresistances of Ag/Co multilayers

We present measurements at 4.2 K of the magnetoresistance (MR) measured with the current perpendicular to the layer planes (CPP) of equal and unequal thickness Ag/Co magnetic multilayers that display giant MR measured with the current in the layer planes (CIP). For Ag layer thicknesses from 2 to 60 nm, and Co thicknesses from 6 to 15 nm, the CPP MR extends up to nearly 50% and ranges from 3 times to more than 10 times as large as the CIP MR for the same samples.