  Spin injection and detection are very sensitive to the interface properties
between ferromagnet and semiconductor. Because the interface properties such as
a tunneling resistance can be chosen independently between the injection and
detection sides, the magnetic transport properties are considered to depend on
the asymmetry of the two interfaces. We theoretically investigate the effect of
the asymmetric interfaces of the injection side and the detection side on both
the local and non-local magnetoresistance measurements. The results show the
magnetoresistance ratio of local measurement structure has its maximum at the
symmetric structure, and the effect of the asymmetry is very weak for the
non-local measurement structure.
