EFFECT OF Co–Ga PAIRED SUBSTITUTION ON SUPERCONDUCTIVITY IN YBa2Cu3O7-δ

Abstract

The effect of Co–Ga paired substitution on the superconducting properties of YBa 2 Cu 3 O 7-δ (Y-123) has been investigated by X-ray diffraction, ac susceptibility, dc resistivity and oxygen content measurements. We report in this paper the results of our studies on the paired substitution of a magnetic and non-magnetic ion at Cu site in Y-123, while keeping the total dopant concentration fixed. The simultaneous substitution of Co and Ga at Cu site shows variation in the transition temperature (T c ), oxygen content and hole concentration as a function of change in the balance of magnetic (Co) and non-magnetic (Ga) concentration. Orthorhombicity (D), given as (b-a)/a, also varies as a function of increasing dopant concentration. The variation in T c due to Co–Ga substitution is discussed in the light of dopant valency and hole filling mechanism.