Raman studies on single-phasic HgBa2CuO4+δ superconductors

Abstract

Polycrystalline samples of HgBa2CuO4+δ superconductors were prepared by solid state reaction of HgO and Ba2CuO3+x precursor in an evacuated silica tube. The HgBa2CuO4+δ has a Tc of 92 K and has a tetragonal cell (P 4/mmm) with lattice parameters a and c with the values of 3.8868 (2) Å and 9.4886 (1) Å, respectively. Raman spectra of polycrystalline HgBa2CuO4+δ show four peaks at 108 cm-1, 158 cm-1, 570 cm-1 and 592 cm-1. Using a factor group analysis and Raman spectral data of the cuprate superconductors, these modes are assigned as Eg and A1g modes of Ba atoms and O(2) oxygens. The higher peaks at 570 cm-1 and 592 cm-1 are assigned to Eg and A1g modes of O(2) oxygen, respectively. The lower two modes at 108 cm-1 and 158 cm-1 are ascribed to vibrations of Ba atoms. Details of mode assignments are discussed based on symmetry and local structure. © 1993.