CONDUCTANCE AND GIANT MAGNETOCONDUCTANCE OF CO-VERTICAL-BAR-CU-VERTICAL-BAR-CO SPIN VALVES - EXPERIMENT AND THEORY

We present measurements of the conductance and magnetoconductance,cl a s a function of cobalt layer thickness for cobalt-copper-cobalt spin v alves deposited by magnetron sputtering,a. We compare these measuremen ts to calculations of the conductance and magnetoconductance , which a re based on first-principles calculations of the self-consistent elect ronic structure of the cobalt-copper-cobalt system. The calculations a re performed using a generalized Kubo formula for the: nonlocal layer dependent conductivity, which is implemented within the layer Korringa -Kohn-Rostoker method for electronic-structure calculations. The scatt ering rates within each layer are adjusted phenomenologically to be co nsistent with the experimentally observed resistivity of thick films o f cobalt and copper. The magnetoconductance and its dependence on the thickness of the cobalt layer are consistent with calculations that in clude strong but spin-dependent scatter inp within the cobalt layers a nd possibly some channeling of electrons in the copper layer. We find that the transmission and reflection of electrons al the interfaces ar e strongly spin dependent and that it is not necessary to invoke addit ional diffuse spin-dependent scattering al the interfaces to explain t he conductance and magnetoconductance of these samples.