Anisotropic Upper Critical Field in Nd1.85Ce0.15CuO4±δ Superconducting Thin Films

Abstract

Thin films of superconducting Nd_1.85Ce_0.15CuO_4±δ were synthesized by a pulsed laser deposition method followed by ex situ annealing in an argon atmosphere. Structural, morphological and electrical characterizations were performed using X-ray diffraction, scanning electron microscopy and temperature-dependent resistivity measurements respectively. X-ray analysis reveals preferential orientation in (001) and (110) directions for the thin films. Resistivity measurements demonstrated a pronounced superconducting behavior in the argon annealed thin films. The critical superconducting properties, the upper critical field and critical current density, were investigated using magneto-transport and magnetization measurements. The anisotropic coefficient which is the ratio of the upper critical field parallel and perpendicular to that of ab plane has been assessed highlighting the significant anisotropy of the Nd_1.85Ce_0.15CuO_4±δ superconductor. The analysis of the activation energy reveals the three-dimensional nature of the vortex lattice in this system.