Spin-current injection and detection in strongly correlated organic conductor

Spin-current injection into an organic semiconductor $\kappa \text{-}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}\text{-}\mathrm{T}\mathrm{T}\mathrm{F}{)}_2\mathrm{C}\mathrm{u}[\mathrm{N}(\mathrm{C}\mathrm{N}{)}_2]\mathrm{B}\mathrm{r}$ film induced by the spin pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage signal was found to appear in the $\kappa \text{-}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}\text{-}\mathrm{T}\mathrm{T}\mathrm{F}{)}_2\mathrm{C}\mathrm{u}[\mathrm{N}(\mathrm{C}\mathrm{N}{)}_2]\mathrm{B}\mathrm{r}$ film. Magnetic-field-angle dependence measurements indicate that the voltage signal is governed by the inverse spin Hall effect in $\kappa \text{-}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}\text{-}\mathrm{T}\mathrm{T}\mathrm{F}{)}_2\mathrm{C}\mathrm{u}[\mathrm{N}(\mathrm{C}\mathrm{N}{)}_2]\mathrm{B}\mathrm{r}$. We found that the voltage signal in the $\kappa \text{-}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}\text{-}\mathrm{T}\mathrm{T}\mathrm{F}{)}_2\mathrm{C}\mathrm{u}[\mathrm{N}(\mathrm{C}\mathrm{N}{)}_2]\mathrm{B}\mathrm{r}$/YIG system is critically suppressed around 80 K, around which magnetic and/or glass transitions occur, implying that the efficiency of the spin-current injection is suppressed by fluctuations which critically enhanced near the transitions.