Magnetoresistance in rf-sputtered(nife/cu/co/cu) spin-valve multilayers

Abstract

A study of the vtiation of the magnetoresistancein (Ni80Fe20/Cu/Co/Cu) multilayers with the thicknesses tNiFe, tcO, and &;cu of each type of component layer has been performed. The magnetoresistance (MR), which at 4 .2 K is larger than 20% for many samples, has been measured for fields applied both parallel and perpendicular to the current. This allows a direct measurement of the anisotropic magnetorestistance as well as an estimate of the spin-valve contribution to the total MR. The dependence of the MR on tcu indicates the presence of an oscillatory interlayer exchange c.oupling through the Cu layers with a period of about 12 Å. The dependence of the MR on tNiFe and tcO was studied at tcu=50 Å, for which the coupling is negligible. In this limit, the variation of the MR is dominated by the thickness dependenceo f the NiFe and Co component layer coercivitie-s, which determine the degree of antiparallel alignement obtained during magnetization reversal.