Large Inverse Spin Hall Effect in Co-Tb Alloys due to Spin Seebeck Effect

Using samples of ${\mathrm{Co}}_{100\ensuremath{-}x}{\mathrm{Tb}}_{x}/\mathrm{Cu}/{\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$, we investigate the heat-to-charge current conversion phenomena in amorphous ${\mathrm{Co}}_{100\ensuremath{-}x}{\mathrm{Tb}}_{x}$ alloys. We find an enhancement of the inverse spin Hall voltage owing to the $\mathrm{Tb}$ impurity by means of the spin Seebeck effect. The spin Hall angle of ${\mathrm{Co}}_{68}{\mathrm{Tb}}_{32}$ is 3.5 times larger than that of $\mathrm{Co}$, and mainly originates from the extrinsic spin Hall effect. Meanwhile, we detect an anomalous Nernst voltage owing to the magnetic properties of ${\mathrm{Co}}_{100\ensuremath{-}x}{\mathrm{Tb}}_{x}$ alloy. The sign of the inverse spin Hall voltage is observed to be the same for all ${\mathrm{Co}}_{100\ensuremath{-}x}{\mathrm{Tb}}_{x}$ samples, whereas the anomalous Nernst voltage changes its sign around the magnetization compensation composition. Our finding proves ${\mathrm{Co}}_{100\ensuremath{-}x}{\mathrm{Tb}}_{x}$ is an efficient spin-to-charge current convertor, and it has advantages for manipulating not only the inverse spin Hall effect but also the anomalous Nernst effect by means of adjusting the $\mathrm{Tb}$ concentration.