Effect of Local Disorder on the Transport Properties of Al-Doped SmBa2Cu3O6+δ Superconductors

In this work we present the investigation of the structural disorder induced by Al doping in SmBa2Cu2.67Al0.33O6+delta superconductors in direct correlation with their transport properties. The interest in such superconducting materials lies in the possibility of extending the delta range of the underdoped region of REBa2Cu3O6+delta superconductors, where phenomena such as pseudogap and superconducting diamagnetic fluctuations above T-C appear. The pair distribution function analysis of high-resolution powder diffraction data has shown that local distortions are present in the proximity of the Al dopant ions. Disorder spreads to the superconducting Cu2-O3 planes producing corrugations in these planes, associated with a decrease of superconducting charge carriers. Conductivity and magnetization measurements have demonstrated that Al-doping affects the charge transport mechanism: Anderson localization and superconductivity coexist, and the T and delta superconducting domains are strongly reduced. Al doping allows not only controlling chemically the charge carrier concentration but also the potential fluctuations within the Cu2-O2/3 planes and appears to be a powerful tool for the investigation of the underdoped zone of REBa2Cu3O6+delta superconductors.