57Fe M�ssbauer study of YBa4Cu2.95Fe0.05O8.5+y

Abstract

Abstract. 57Fe Mtssbauer measurements were performed on the Fe-doped YBa4Cu3Os.5+y compound as a function of annealing temperature in vacuum. Mtssbauer spectra were analyzed using three different quadrupole split doublets. The resistance measurements showed that the compound is not superconducting. The possible identification of the Cu sites with their nearest neighbor oxygen sites in this compound is suggested. Comparison of the results with data of the presence of the superconductor YBa2Cu30 7 allows us to suppose that the presence of the Cu-chain sites alone does not result in superconductivity.PACS: 74.70.Vy, 76.80.+yThe discovery of high-T~ superconductivity in the YBa2Cu307 (named 1-2-3) compound has stimulated considerable effort to identify the different compounds and phases in the YzO-BaO-CuO system [-1, 2]. Most of them have been identified and possible crystal structures presented. For one of them, YBa4Cu308.5+ r (named 1-4:3), the positions and occupation numbers of especially the oxygen ions were determined by neutron powder diffraction measurements [2]. In contrast to the 1-2-3 compound, in the 1-4-3 structure there are only Cu-chain sites along all three crystallographic axes.In this report the Mtssbauer study of the Fe-doped 1-4-3 compound is presented as a function of annealing temperature in vacuum. Comparing the obtained results with data for the 1-2-3 compound we attempted to establish the role of Cu-chain and Cu=plane sites in the high-To superconducting transition. It is shown that the presence of Cu-chain sites alone does not result in superconductivity.