Raman phonons in ReOFeAs (Re= Sm, La)

Abstract

We report the polarized Raman spectra of undoped ReOFeAs (Re = Sm, La) collected at room temperature from $ab$ surfaces of impurity free microcrystals. The spectra exhibit sharp phonon lines on very weak electronic scattering background. The frequency and symmetry of the four Raman phonons involving out-of-plane atomic vibrations are found at 170 cm-1 (A1g, Sm), 201 cm-1 (A1g, As), 208 cm-1 (B1g, Fe), 345 cm-1(B1g, O) for SmOFeAs, and 162 cm-1 (A1g, La), 208 cm-1 (A1g, As), 201 cm-1 (B1g, Fe), 316 cm-1 (B1g, O) for LaOFeAs.