  We present a systematic study of the structure and lattice dynamics at room
temperature, and the phonon behavior at low temperatures in orthorhombic
Gd$_{1-x}$Y$_{x}$MnO$_{3}$ manganites, with 0 $\leq$ x $\leq$ 0.4, using powder
x-ray diffraction and Raman scattering. A thorough analysis towards the
correlation between both structural and Raman modes parameters was undertaken.
The data obtained at room temperature reveal structural distortions arising
from the Jahn-Teller distortion and octahedra tilting. The Jahn-Teller
distortion is apparently x-independent, while an increase of Mn-O1-Mn bond
angle of about 0.5{\deg} could be ascertain when x changes from 0 to 0.4.
Spin-phonon coupling was evidenced from the Raman results. The temperature
dependence of the B1g in-plane O2 stretching mode of the MnO6 octahedron has
revealed either a positive or negative shift regarding the pure anharmonic
temperature dependence of the phonon frequency, which strongly depends on the
Y-concentration. The frequency renormalization is explained in terms of a
competition between ferro and antiferromagnetic interactions. The ratio between
the spin-phonon coupling constant and the effective magnetic exchange integral
per spin was determined from the renormalized wave number of the in-plane O2
stretching mode, associated with the spin-spin correlation function.
