Raman studies of TGS doped with Nd

Monocrystals of triglycine sulfate (TGS) doped with Nd, were studied by Raman spectroscopy. HeNe laser radiation (632.817 nm) was used as the illumination source. The spectra were dispersed with a resolution of 1 cm^-1/pixel. The observed lines were assigned to the vibrations of the characteristic groups and valence bonds in the investigated samples. Doping of TGS with Nd does not cause a change in the crystal structure and the symmetries of groups in the unit cell remain unaffected. A new mode at 1535 cm^-1 appeared for all crystals doped with Nd, which indicates that Nd is coordinated with the glycine molecule. Doping with Nd affects significantly the C-CO bending mode at 584 cm^-1, the O-C-O bending mode at 665 cm^-1, the SO₄^2- mode at 1086 cm^-1 and the CH₂ wagging and twisting mode at 1310 cm^-1. The Raman bands at 1374 and 1413 cm^-1 indicate the presence of a zwitterion, which supports Hoshino's theory for spontaneous polarization reversal in TGS.