Theory of Spin Loss at Metallic Interfaces

Interfacial spin-flip scattering plays an important role in magnetoelectronic devices. Spin loss at metallic interfaces is usually quantified by matching the magnetoresistance data for multilayers to the Valet-Fert model, while treating each interface as a fictitious bulk layer whose thickness is delta times the spin-diffusion length. By employing the properly generalized circuit theory and the scattering matrix approaches, we derive the relation of the parameter d to the spin-flip transmission and reflection probabilities at an individual interface. It is found that d is proportional to the square root of the probability of spin-flip scattering. We calculate the spin-flip scattering probabilities for flat and rough Cu/Pd interfaces using the Landauer-Buttiker method based on the fir-principles electronic structure and find d to be in reasonable agreement with experiment.