  The underlying physics of the inverted Hanle effect appearing in Si was
experimentally investigated using a Si spin valve, where spin transport was
realized up to room temperature. No inverted-Hanle-related signal was observed
in a non-local 4-terminal scheme even the same ferromagnetic electrode was
used, whereas the signal was detected in a non-local 3-terminal scheme.
Although the origin of the inverted Hanle effect has been thought to be
ascribed to interfacial roughness beneath a ferromagnetic electrode, our
finding is inconsistent with the conventional interpretation. More importantly,
we report that there were two different Hanle signals in a non-local 3-terminal
scheme, one of which corresponds to the inverted Hanle signal but the other is
ascribed to spin transport. These results strongly suggest that (1) there is
room for discussion concerning the origin of the inverted Hanle effect, and (2)
achievement of spin transport in a non-local 4-terminal scheme is indispensable
for further understanding of spin injection, spin transport and spin coherence
in Si. Our new findings provide a new and strong platform for arising
discussion of the physical essence of Hanle-related spin phenomena.
