Quantum and thermal creep in Pr1.85Ce0.15CuO4+δ single crystals

Abstract In order to investigate the vortex dynamics of a high-T c superconductor at fields up to B c2 , single crystals of the electron doped superconductor Pr 1.85 Ce 0.15 CuO 4+δ are oxygen doped in such a way that 6 T c2 (T=0) c in magnetic fields up to 7 T using high sensitivity torque magnetometry. For T ∼ 0.1 K the results are compared with a quantum creep theory for the firty limit. In the thermal regime data are analysed in terms of an activation energy U(j s ) = (U c /μ)[(j c /j s ) μ −1].