Interplay of antiferromagnetic coupling in copper/permalloy combination multilayers

The evolution of the giant magnetoresistance (GMR) effect in sputtered comb ination multilayers (CMLs) of type Py-1.8nm//{(Cu-1.8nm/Py-1.6nm)(N)/(Cu-0. 9nm/Py-1.6nm)(N)}(y) with Py (permalloy=Ni81Fe19) has been investigated at room temperature. It is shown that the GMR characteristic of these CMLs can be phenomenologically predicted, if the physical properties are known, i.e ., the GMR effect amplitude, double layer conductance, and bilinear and biq uadratic antiferromagnetic exchange coupling constants of the two underlyin g {Cu/Py}(N) base systems at the first (Cu-0.9nm) and second (Cu-1.8nm) ant iferromagnetic coupling maximum (AFCM). The GMR characteristic of the simpl est CML with N = 1 is, e.g., determined by averaging the bilinear and biqua dratic exchange coupling constants of the two base systems. The GMR charac teristics of CML with N greater than or equal to 2 are a superposition of t hat of the underlying {Cu/Py}(N) base systems weighted by the fraction of t he corresponding double layer conductance. Furthermore, it is demonstrated that the CMLs are interesting from an application point of view since they combine the temperature stability of the underlying {Cu/Py}(N) base system at the second AFCM with a larger GMR effect amplitude. (C) 2000 American In stitute of Physics. [S0021-8979(00)57908-0].