  We study spin-scattering asymmetry at the interface of two ferromagnets (FMs)
based on a half-metallic Co$_{2}$Fe$_{0.4}$Mn$_{0.6}$Si (CFMS)/CoFe interface.
First-principles ballistic transport calculations based on Landauer formula for
(001)-CoFe/CFMS/CoFe indicate strong spin-dependent conductance at the
CFMS/CoFe interface, suggesting a large interface spin-scattering asymmetry
coefficient ($\gamma$). Fully epitaxial current-perpendicular-to-plane giant
magnetoresistance (CPP-GMR) pseudo-spin-valve (PSV) devices involving
CoFe/CFMS/Ag/CFMS/CoFe structures exhibit an enhancement in MR output owing to
the formation of the CFMS/CoFe interface at room temperature (RT). This is well
reproduced qualitatively by a simulation based on a generalized two-current
series-resistor model with considering the presence of $\gamma$ at the
CFMS/CoFe interface, half-metallicity of CFMS, and combinations of terminated
atoms at the interfaces in the CPP-GMR PSV structure. We show direct evidence
for a large $\gamma$ at a half-metallic FM/FM interface and its impact on
CPP-GMR effect even at RT.
