Magnetic multilayers of Fe/Au: role of the electron mean free path

The giant magnetoresistance (GMR) was measured for Fe/Au magnetic multilaye rs in both the CIP and CPP configurations, for a series of samples each hav ing the same thickness for the Fe layers (10 Angstrom) but a different thic kness for the Au layers (in the range 20-50 Angstrom). It was found that th e GMR is only a few per cent in the CIP configuration, whereas the GMR rang es from 20 to 80% in the CPP configuration. We attribute this order-off-mag nitude difference in the values of the GMR for the two configurations to th e short electron mean free path, resulting from the relatively high resisti vity of these multilayers. A short electron mean free path reduces sharply the value of the GMR in the CIP configuration, while leaving unchanged the value of the GMR in the CPP configuration.