Raman modes ofRNi2B2C (R=Lu, Ho, Y) single crystals

Results of Raman measurements on R${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C (R=Lu, Ho, Y) single crystals are reported. Raman peaks are observed at 190 ${\mathrm{cm}}^{\mathrm{-}1}$ and near 830 ${\mathrm{cm}}^{\mathrm{-}1}$. From the polarization-dependence measurements, these peaks are assigned to be the Ni-${\mathit{B}}_{1\mathit{g}}$ and the B-${\mathit{A}}_{1\mathit{g}}$ modes, respectively. Raman study on the effects of boron isotope ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ substitution for ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ in the ${\mathrm{LuNi}}_2$ ${\mathrm{B}}_2$C crystals confirms that the mode near 830 ${\mathrm{cm}}^{\mathrm{-}1}$ is due to the vibration of B atoms. However, from these single crystals, the expected Ni-${\mathit{E}}_{\mathit{g}}$ and B-${\mathit{E}}_{\mathit{g}}$ modes are not observed. © 1996 The American Physical Society.