Specific Resistance of Pd/Ir Interfaces

In electronic transport with current-flow perpendicular to the layer planes (CPP) of a metallic multilayer, the interface specific resistance AR (area A through which CPP-current flows times sample resistance R) is fundamental. Special interest focuses upon AR for metals M1 and M2 with the same crystal structure, and lattice parameters the same to within $\sim $ 1 percent, as AR can then be calculated with no free parameters. From measurements of the total AR of sputtered Pd/Ir multilayers, we obtain twice the interface specific resistance, 2AR$_{Pd/Ir}$ = 1.02 $\pm $ 0.06 f$\Omega$ m$^{2}$. For a single fcc structure with average lattice parameter of Pd and Ir, calculations including only spd orbitals give for perfect interfaces, 2AR$_{Pd/Ir}$(Perf) = 1.21 $\pm $ 0.1 f$\Omega $m$^{2}$, and for interfaces composed of two monolayers of a random 50{\%}-50{\%} alloy, 2AR$_{Pd/Ir }$(50/50) = 1.22 $\pm $ 0.1 f$\Omega $m$^{2}$. These values fall just outside the range of the experimental value. Upgrading to include f-orbitals gives 2AR$_{Pd/Ir}$(Perf) = 1.1 $\pm $ 0.1 f$\Omega $m$^{2}$ and 2AR$_{Pd/Ir}$(50-50) = 1.15 $\pm $ 0.1 f$\Omega $m$^{2}$. Within mutual uncertainties, these values are compatible with the experimental one.