Low temperature fluxline relaxation effects in YBa2Cu3O7−δ thin films

Abstract

We have investigated magnetic flux relaxation at low temperatures in a 90 nm epitaxial coevaporated film on YBa2Cu3O7−δ superconductor. This film is characterized by a high critical current Jc of 3.5 × 1011Am−2 at 4.2 K, and 1.3 × 1010Am−2 at 77 K. Although Jc depends strongly on the applied magnetic field B the magnetic relaxation is only weakly dependent on B. Also the magnetic relaxation does not vanish at zero temperature, indicating that besides a thermally activated process there is another intrinsic process working.