The effect of calcium substitution in deoxygenated R1−xCaxBa2Cu3O6.1 systems (R=Y, Eu): appearance of superconductivity, insulator to metal transition

The changes in crystallographic, magnetic, and transport properties with Ca substitution in deoxygenated R1-xCaxBa2Cu3O6.1 (R=Y, Eu) system have been investigated. The superconductivity is induced at a Ca content of x=0.26-0.3. However, induced superconductivity exhibits a low critical field. The system R1-xCaxBa2Cu3O6.1 undergoes an insulator to metal transition. The increase in the effective magnetic moment with Ca substitution is detected. The crystal structure undergoes slight modifications. Although, the observed variation of crystal structure forced by Ca doping does not reproduce the structure modifications characteristic of O doping. Changes in properties of R1-xCaxBa2Cu3O6.1 should be related to hole doping, observed as an increase in formal Cu valence, which was confirmed by iodometric titration. 29 refs.