To clarify spin-related phenomena within a single conduction valley of multivalley semiconductors, we experimentally study the effect of carrier concentration $\left(n\right)$ on spin lifetime $\left({\tau }_{\mathrm{S}}\right)$ in strained ${\mathrm{Si}}_{0.1}{\mathrm{Ge}}_{0.9}$ at various temperatures. The spin diffusion length $\left(\lambda \right)$ of strained ${\mathrm{Si}}_{0.1}{\mathrm{Ge}}_{0.9}$ is estimated from the contact distance dependence of the nonlocal spin signals for spin transport measurements in lateral spin-valve devices with varying $n$. The obtained $\lambda$ is found to depend on $n$ at temperatures below $\sim 100\mathrm{K}$, with the estimated ${\tau }_{\mathrm{S}}$ value at 8 K varying significantly with $n$, ranging from 0.2 to 6.2 ns. These features suggest the presence of intravalley spin scattering at low temperatures even in doped multivalley semiconductors. Thus, strained $n\text{−}{\mathrm{Si}}_{0.1}{\mathrm{Ge}}_{0.9}$ with $L$-valley energy splitting serves as a powerful tool for investigating the spin relaxation mechanisms in a single conduction valley of doped multivalley semiconductors.

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• Spin diffusion
• Spin relaxation
• Elemental semiconductors
• Spin valves