Production and identification of flux-pinning defects by electron irradiation in YBa2Cu3O7-x single crystals

Abstract

An enhancement in Jc of YBa2Cu3O7-x single crystals in a magnetic field is observed after irradiation with 1-MeV electrons. Typically, a factor-of-2 increase in Jc is deduced from magnetic hysteresis loops at 10 K and 1 T with Hc. This enhancement is about 1/2 of that produced by proton and neutron irradiations under similar measurement conditions. In situ transmission- electron-microscopy studies found no visible defects induced by electron irradiation, which means that point defects or small clusters (of size <2 nm) are responsible for the extra pinning. Annealing studies suggest that effective pinning centers for Hc do not include oxygen vacancies in the Cu-O chains. Based on calculations of cross sections for displacements on the different sublattices, and in conjunction with the results of a Jc calculation by Kes, we suggest that the most likely pinning defect is the displacement of a Cu atom from the CuO2-plane sites. © 1992 The American Physical Society.