Reduction of flux creep in spite of a j c decrease in YBa2Cu3O7−δ after neutron irradiation

Publisher Website
Google Scholar
Abstract
YBa2Cu3O7−δsingle crystals with T c =90.5 K and different transition width have been irradiated with fast neutrons (E≳0.1 MeV) and a fluence of Φ⋅t=2×1017 cm−2. The flux‐creep dM/dlnt at B=0.5 T is reduced at any temperature up to T=60 K by a factor of about 2. Correspondingly, the effective pinning potential U eff is enhanced up to 100k BT at low temperatures and 50k BT at T=77 K, independent of an increase or decrease of the magnetization current density after irradiation. Therefore, the enhancement of U eff may not in every case be related to a j c increase, which is also determined by the number of pinning centers or a certain defect structure, which may not necessarily show deep pinning potentials. The results can be explained within the conventional flux creep theory and are in a good agreement with recent considerations of the role of electronic anisotropy in the dissipative behavior of YBa2Cu3O7−δ.