Raman study of the high-Tcsuperconductors ABa2Cu3O7-x(A=Y, Ho, Y0.1Gd0.9and Y0.9Sm0.1)

Abstract
The Raman spectra of polycrystalline A-Ba-Cu-O (A=Y, Ho, Y0.1Gd0.9 and Y0.9Sm0.1) are studied from 200 to 800 cm-1 at room temperature. To distinguish the Cu-O modes of the A-Ba-Cu-O systems, the Raman spectrum of the Ho-Ba-Ni-O system is also recorded. The assignment of the observed bands has been made by comparing spectra of these samples and on the basis of the information available in the literature. The mode at 338 cm-1, which shows anomalous behaviour at the superconducting transition temperature, is assigned to the Cu-O mode of the ABa2Cu3O7-x compound. The other bands observed have been assigned to different phases present in these samples.