  We show a marked effect of the magnetic domain structure in an epitaxial CoFe
contact on the spin accumulation signals in Si detected by three-terminal
Hanle-effect measurements. Clear reduction in the spin accumulation signals can
be seen by introducing the domain walls in the CoFe contact, caused by the
lateral spin transport in the Si channel. The domain walls in the CoFe contact
largely affect the spin lifetime and bias-current dependence of the spin
signals. These results indicate that the estimation of the spin related
properties without considering the domain structure in the contact causes
non-negligible errors in the three-terminal Hanle-effect measurements.
