Investigation of the inverted Hanle effect in highly doped Si

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 nonlocal four-terminal scheme, even when the same ferromagnetic electrode was used, whereas the signal was detected in a nonlocal three-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 nonlocal three-terminal scheme, one of which corresponds to the inverted Hanle signal while 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 nonlocal four-terminal scheme is indispensable for further understanding of spin injection, spin transport, and spin coherence in Si. Our findings provide a strong platform for future discussion of the physical essence of Hanle-related spin phenomena.