Effect of oxygen content on carrier localization and ion-cluster effect for the Fe-doped YBCO system

Abstract

The oxygen content, Hall coefficient and superconductivity are systematically studied on YBa2Cu3-xFexOy(x=00, 01 , 02) and YBa2Cu2.8Fe0.2Oy(y=705—653) systems. The results show that ox ygen content has a great influence on the transport and transfer of carriers and the superconductivity of the samples, the suppression of Tc caused b y Cu( 1) site substitution could be weakened by the increase of oxygen content to some extent. The carrier (holes) density in CuO2 plane plays a key role i n affecti ng the superconductivity. Based on the charge transfer model, and considering th e carrier localization and ion-cluster effect resulting from Fe substitution on Cu(1) site, we have discussed the change of carrier density caused by the oxygen content and Fe doping concentration. It proves that with the increase of Fe dop ing concentration or the decrease of oxygen content (for the same doping concent ration), the efficient oxygen vacancy increases, which enhances the ion-cluster effect and the carrier localization effect, resulting in the decrease of carrier density that participats in superconducting transport in the CuO2 pl ane, and accordingly, the decrease of Tc.