  Combined measurements of normal and inverted Hanle effects in
CoFe/MgO/semiconductor (SC) contacts reveal the effect of spin relaxation rate
on the interfacial spin depolarization (ISD) from local magnetic fields.
Despite the similar ferromagnetic electrode and interfacial roughness in both
CoFe/MgO/Si and CoFe/MgO/Ge contacts, we have observed clearly different
features of the ISD depending on the host SC. The precession and relaxation of
spins in different SCs exposed to the local fields from more or less the same
ferromagnets give rise to a notably different ratio of the inverted Hanle
signal to the normal one. At room temperature, a large ISD is observed in the
CoFe/MgO/Si contact, but a small ISD in the CoFe/MgO/Ge contact. The ISD of the
CoFe/MgO/Ge contact has been substantially increased at low temperature. These
results can be ascribed to the difference of spin relaxation in host SCs. A
model calculation of the ISD, considering the spin precession due to the local
field and the spin relaxation in the host SC, explains the temperature and bias
dependence of the ISD consistently.
