Raman spectra of YBa 2Cu 3−xM xO y( M= Co, Ni) superconductors

Abstract

Raman spectra of tetragonal YBa 2Cu 3−xCo xO y which contains oxygen disorder as well as orthorhombic YBa 2Cu 3O y and YBa 2Cu 3−xNi xO 7 were recorded. With Co doping, a broad band appears at 573 cm −1, the 500 cm −1 band of orthorhombic YBa 2Cu 3O y decreases in frequency, and the 115 cm −1 band disappears. The origin of the 573 cm −1 band can be attributed to the infrared active Cu-O stretching mode which becomes Raman active due to the oxygen disorder. The latter two indications are the same as those in the case of oxygen deficient tetragonal phase. Mode patterns of observed Raman bands of orthorhombic YBa 2Cu 3O y are also discussed.