Measurements of the surface critical current of YBa2Cu3O7−δ thin films: Probing the nonuniformity of their superconducting critical temperature along the c-axis

Abstract

The existence of nonsuperconducting zones in YBa2Cu3O7−δ (YBCO) films below the transition temperature to the nonresistive state can limit the performances of YBCO devices. In this work, we present detailed measurements of the temperature dependence of the critical surface current density of c-axis oriented epitaxial YBCO films, that suggest that their superconducting critical temperature, Tc, is modulated along the c-axis. This nonuniformity of Tc, that could be present in all YBCO films, seems also to be supported by measurements of both the field cooled in-plane magnetic moment and the oxygen content (by non-Rutherford elastic resonance scattering) of some samples.

Joining Superconducting MgB2 Parts by Spark Plasma Sintering: A New Technique with High Potential for Manufacturing Future Superconducting Devices

“…While thin films [5] and powders [6] show anisotropic superconducting properties, sintered ceramics are isotropic. One of the main advantages of MgB 2 is its simple stoichiometry in opposition to that of high temperature oxide superconductors such as YBa 2 Cu 3 O 7 , the superconducting properties of which are strongly dependent on the oxygen content [7]. It includes cheap and non-toxic elements and shows a high mechanical hardness of about 12.5 GPa [8].…”

A New Technique for the Determination of the Critical Current Density in Superconducting Films and Flat Samples

“…This is especially detrimental in the case of the coated conductors, whose characterization is seldom carried out far below 77 K, while their very large critical current density at low temperature is interesting for many applications. We have proposed for some time a technique suitable for square films [2,3], based on the measurement of the magnetic moment generated by the current lines persisting in the sample after the application of a magnetic field. Typically with this technique, using a SQUID magnetometer, the measurements time in the whole range of the temperatures below T c with a 1 K interval is of 2 hours.…”