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

The room temperature phonon modes of the isostructural (Nd,Yb):Y_xGd_1−x(VO₄) laser crystals were determined using the Raman scattering technique, and the observed wavenumbers follow the overall mode distribution expected for REVO₄ (RE=rare earth) compounds with the tetragonal zircon structure, . They were assigned according to the group theory in terms of the internal modes of the VO₄ tetrahedron and the external modes of the Y_xGd_1−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):Y_xGd_1−x(VO₄) shifts upwards (one-phonon-like behavior) when Y replaces for Gd.