Junctions between these layers plays an essential role in controlling the spin current. Many of these devices rely on spin-orbit coupling, which can cause spins to rotate or flip. Spin flip scattering at the interface thus plays an important role in these devices. Scattering is usually deleterious to device operation because it results in loss of spin coherence that underpins the device. This loss is typically quantified experimentally by measuring an empirical parameter . It was widely assumed that was proportional to the spin-flip scattering probability of an individual interface.
In a recent paper PRL 117, 207204 we show that is proportional to the square root of the spin flip scattering probability, rather than the probability itself. To buttress the theory, direct calculations of spin flip loss where calculated for the Cu/Pd interface within the Landauer-Büttiker formalism, using the lmpg code.
The figure shows spin-conserving and spin-flip transmittances T↑↑ and T↑↓ and corresponding reflectances R↑↓, R↑↓ for the Cu/Pd (111) interface, calculated by lmpg. The direct calculations of δ matched measurements reasonably well.