A Raman study of the structural properties of YBa2(Cu1 − xFex)3Oy

Abstract The effects of Fe-substitution of YBa 2 Cu 3 O y have been investigated by means of Raman scattering, X-ray diffraction, resistivity and susceptibility measurements. A series of samples of YBa 2 (Cu 1 − x Fe x ) 3 O y with different dopant concentration (0 ⩽ x ⩽ 0.15) has been prepared in two batches, the second set having undergone twice the heat and mechanical treatment used to produce the first batch. Considerable improvement in the superconducting transition temperature, T c , is obtained upon reprocessing. A phase transformation from orthorhombic to tetragonal symmetry is observed for x =0.05 from the X-ray measurements in agreement with previous work. Using a micro-Raman technique, all five A g vibrational modes have been measured and their dependence on Fe-concentration is analyzed. There are indications that iron substitutes for copper at both sites and that the structure is a mixture of orthorhombic and tetragonal microdomains for all x .