Vortex dynamics study on an uniaxially textured YBCO/MgO superconducting film from magnetic measurements

Abstract The vortex dynamics of an undoped uniaxially textured YBa 2 Cu 3 O 7−δ (YBCO) superconducting film grown onto a MgO (100) substrate was inspected by applying the vortex glass and collective-pinning models. The texture and structural characterization studied by X-ray diffraction revealed a uniaxially (00 l) YBCO layer, which coexists with minor Y 2 BaCuO 5 and CuO phases. The temperature dependence of the magnetization in the superconducting state revealed a critical temperature T C = 88 K. By measuring the hysteresis loops ( M ( H ) ) at 10–70 K, the critical fields H C 1 , H C 2 , H P and H irr were estimated and a vortex matter diagram was sketched. By using the Bean model, the critical current density values J C ( T , H ) were obtained and the typical peak effect is observed. The vortex dynamics mechanism is discussed taking into account four vortex feature regimes in the double-logarithmical J C ( H ) curves. The vortex pinning mechanism is discussed by obtaining the pining force, F P , its normalization, f ( h ) , and magnetic relaxation M ( t ) measurements taken in field cooling mode at 10–60 K. The glassy exponent μ and the characteristic energy U ( J ,