Raman and Ftir Spectral Investigations of Twinned M(IO3)2 (M = Mn, Ni, Co, AND Zn) Crystals

Raman and infrared spectra of twinned M(IO3)2 (M = Mn, Ni, Co, and Zn) crystals are recorded and the observed bands are assigned in terms of vibrations of the IO6 octahedron. The IO6 octahedra in Mn(IO3)2 and Zn(IO3)2 are comparatively more distorted than those of Co(IO3)2 and β-Ni(IO3)2. The Iν1/Iν5 ratio of Mn(IO3)2 is higher compared to other compounds, and its linear polarizability is more than that of angular polarizability. The noncentrosymmetric space group of the title compounds is confirmed by the coincidence of the majority of IR and Raman bands, and the compounds giving intense Raman bands are expected to give better SHG efficiency.