Phonons in isostructural (ND,Yb):YxGd1−x(VO4) laser crystals: A Raman scattering study

The room temperature phonon modes of the isostructural (Nd,Yb):YxGd1−x(VO4) laser crystals were determined using the Raman scattering technique, and the observed wavenumbers follow the overall mode distribution expected for RE VO4 (RE =rare earth) compounds with the tetragonal zircon structure, View the MathML sourceD4h19. They were assigned according to the group theory in terms of the internal modes of the VO4 tetrahedron and the external modes of the YxGd1−x(VO4) lattice. No appreciable changes in the phonon wavenumbers were observed for Yb:GdVO4 (Yb=0.008, 0.015, 0.020, 0.025, and 0.035), indicating that the force fields in the GdVO4 lattice are not strongly altered by Yb doping at the Gd site. However, most of the phonon wavenumbers in the systems (Nd,Yb):YxGd1−x(VO4) shifts upwards (one-phonon-like behavior) when Y replaces for Gd.