RAMAN STUDIES ON SINGLE-PHASIC HGBA2CUO4+DELTA SUPERCONDUCTORS

Polycrystalline samples of HgBa2CuO4+delta superconductors were prepar ed by solid state reaction of HgO and Ba2CuO3+x precursor in an evacua ted silica tube. The HgBa2CuO4+delta has a T(c) of 92 K and has a tetr agonal cell (P 4/mmm) with lattice parameters a and c with the values of 3.8868 (2) angstrom and 9.4886 (1) angstrom, respectively. Raman sp ectra of polycrystalline HgBa2CuO4+delta show four peaks at 108 cm-1, 158 cm-1, 570 cm-1 and 592 cm-1. Using a factor group analysis and Ram an spectral data of the cuprate superconductors, these modes are assig ned as E(g) and A1g modes of Ba atoms and O(2) oxygens. The higher pea ks at 570 cm-1 and 592 cm-1 are assigned to E(g) and A1g modes of O(2) oxygen, respectively. The lower two modes at 108 cm-1 and 158 cm-1 ar e ascribed to vibrations of Ba atoms. Details of mode assignments are discussed based on symmetry and local structure.