FT RAMAN-SPECTROSCOPY OF SOME METAL HEXABORIDES

Fourier-transform Raman (FT) spectra of single-crystal LaB6 and SmB6 a nd of sintered EuB6-XCX (X approximate to 0.1) were measured at room t emperature, For excitation a Nd:YAG laser with about 2 W irradiation p ower was used. The spectra exhibited many more details of the phonon d ensities of states than those obtained with conventional Raman spectro scopy by other authors. In particular two low-energy peaks were found at 104 and 204 cm(-1), which can he easily attributed to the acoustica l and the lowest optical branches. The FT Raman spectra of LaB6 agree well with the phonon densities of states determined by other experimen tal methods and theoretical calculation, while for SmB6 a considerable softening of the optical modes is observed, which is probably due to nonlinear effects in consequence of the high excitation power used in the FT Raman spectrometer. (C) 1997 Academic Press.