Local magnetic properties of $Y12Co5Bi$ and $Gd12Co5Bi$ studied by muon spin relaxation

The recently discovered $(RE)12Co5Bi$ (where RE is a rare earth element) system has rich magnetic phase diagrams. We applied muon spin relaxation to study the local magnetism in polycrystalline samples of $Y12Co5Bi$ and $Gd12Co5Bi$⁠. Our results indicate a magnetic transition at around $100K$ for $Gd12Co5Bi$⁠. By contrast, $Y12Co5Bi$ does not show a magnetic transition as expected since $Y3+$ does not contain any $f$ electrons. These results are consistent with the dc susceptibility measurements. We also estimate and discuss the fluctuation rates in the high temperature paramagnetic regime for $Gd12Co5Bi$⁠.