  In this paper the first principle noncollinear transport calculation for
Cu/Co(111) including interfacial spin-flipping was performed. We modeled
spin-flipping at the interface by assuming a noncollinear magnetic structure
with random magnetization orientation which satisfied Gaussian distribution
along average magnetization direction. The relationship between spin-dependent
conductance including interfacial spin-flipping and random magnetization
orientation distribution width was obtained. For certain distribution width,
our defined spin-flipping ratio coincides with the range of experimental
spin-flipping probability $P=1-e^{-\delta}$, where $\delta=0.25\pm0.1$. The
magnetoresistance in Co/Cu/Co spin valve system including interfacial
spin-flipping has also been calculated.
