  We study the impact of spin-active scattering on Andreev spectra of point
contacts between superconductors(SCs) and strongly spin-polarized
ferromagnets(FMs) using recently derived boundary conditions for the
Quasiclassical Theory of Superconductivity. We describe the interface region by
a microscopic model for the interface scattering matrix. Our model includes
both spin-filtering and spin-mixing and is non-perturbative in both
transmission and spin polarization. We emphasize the importance of spin-mixing
caused by interface scattering, which has been shown to be crucial for the
creation of exotic pairing correlations in such structures. We provide
estimates for the possible magnitude of this effect in different scenarios and
discuss its dependence on various physical parameters. Our main finding is that
the shape of the interface potential has a tremendous impact on the magnitude
of the spin-mixing effect. Thus, all previous calculations, being based on
delta-function or box-shaped interface potentials, underestimate this effect
gravely. As a consequence, we find that with realistic interface potentials the
spin-mixing effect can easily be large enough to cause spin-polarized sub-gap
Andreev bound states in SC/sFM point contacts. In addition, we show that our
theory generalizes earlier models based on the Blonder-Tinkham-Klapwijk
approach.
