Thermally activated dissipation in Y 1Ba 2Cu 3O 7−x/Y 1Ba 2(Cu 1−xNi x) 3O 7−x superconducting multilayer thin films

Abstract

Heterostructures of Y 1Ba 2Cu 3O 7− x /Y 1Ba 2(Cu 1− x Ni x ) 3O 7− x superconducting thin films have been grown on (100) yttriumstabilized ZrO 2 substrates using a pulsed laser deposition technique. The thickness of the Y 1Ba 2Cu 3O 7− x layer was changed from 120 Å to 420 Å, and the thickness of the Y 1Ba 2(Cu 1− x Ni x ) 3O 7− x layer was varied from 85 Å to 480 Å, in order to investigate thermally activated dissipation behavior due to flux motion. The resistivity transitions of multilayers have been measured below T c in magnetic fields up to 5 T. The electrical resistivity in magnetic field is thermally activated and shows a broad transition about 4 ∼ 5 K for magnetic field perpendicular to the c-axis and 8 ∼ 10 K for field parallel to the c-axis. The broadening of the resistive transition observed in multilayer thin films is shown to depend on both Y 1Ba 2Cu 3O 7− x and Y 1Ba 2(Cu 1− x Ni x ) 3O 7− x layer thickness for both magnetic fields parallel and perpendicular to the c-axis. The activation energies derived from thermally activated flux flow are proportional to the Y 1Ba 2Cu 3O 7− x layer thickness up to 360 Å, but are inversely proportional to the increase of the Y 1Ba 2(Cu 1− x Ni x ) 3O 7− x layer thickness when the other layers retain the same thickness.