FIRST PRINCIPLES CALCULATIONS OF ELECTRICAL-CONDUCTIVITY AND GIANT MAGNETORESISTANCE OF PERIODIC MULTILAYERS AND SPIN VALVES

We used the Layer Korringa Kohn Rostoker technique to calculate the el ectronic structure of cobalt-copper multilayers and spin valves from f irst principles within the local spin density approximation. Using thi s electronic structure together with a phenomenological self-energy wh ich may vary from layer to layer, we calculated the non-local layer-de pendent conductivity by means of the Kubo linear response formalism. B y calculating the majority the minority conductivities for parallel an d anti-parallel alignment of the moments in the cobalt layers we deter mined the giant magnetoresistance (GMR). Several interesting features emerge from the calculations, When the scattering rates are relatively high, we find that the contributions to the GMR are largely non-local , with the largest contributions arising from changes in the currents carried in a cobalt plane next to copper due to fields sensed in the c obalt layer on the other side of copper. When scattering rates are rel atively low (comparable to that of cobalt and copper at room temperatu re), there are important contributions to the GMR from local conductio n in the copper layers. This effect arises from the fact that when the component of the majority spin electron momentum parallel to the laye rs exceeds a certain value, it gets trapped in the copper layers. If t he scattering rate is lower in the copper than in the cobalt there is a significant enhancement in the majority spin conductivity and in the GMR. This effect if analogous to the channeling of light by an optica l waveguide. (C) 1996 American Institute of Physics.