MAGNETORESISTANCE OF CO CU SUPERLATTICES GROWN BY MOLECULAR-BEAM EPITAXY/

The giant magnetoresistance (GMR) has been investigated for Co/Cu supe rlattices grown by molecular beam epitaxy (MBE) with the copper and co balt (111) planes parallel to the surface. When Au was used as a buffe r layer, values of the GMR were found as high as 30%. Oscillations wer e observed in the saturation magnetic field as a function of the thick ness of the Cu layer, but these oscillations were not observed in the GMR. The central purpose of the investigation was to study the effect on the GMR of annealing the superlattices and to interpret the changes in terms of the relative contributions to the resistivity of bulk and interface electron scattering. It was found that the magnitude of the GMR for the Co/Cu system decreases on annealing in sharp contrast to previous observations in Fe/Cr superlattices for which several workers have shown that the effect of annealing was normally to increase the GMR. This striking difference between the two systems is explained in terms of their very different spin dependence for interface electron s cattering. A calculation is presented which accounts quantitatively fo r both our results for the Co/Cu system, and for the contrasting resul ts in Fe/Cr.