Critical current densities and transport in superconducting YBa2Cu3O7−δ films made by electron beam coevaporation

Abstract

Thin films of the high Tc superconductor YBa2Cu3O7−δ were prepared and characterized. The films made on SrTiO3 showed epitaxial growth and high critical current densities in excess of 9×104 at 78 K and 2×106 at 4.2 K. Also, surface pinning in the parallel direction was found to be very high. The measurements put a lower limit on the depairing critical current density of 5×107 A/cm2.

Preparation of Y-Ba-Cu-O thin films by laser evaporation with near-infrared radiation

“…Superconducting Y-BaCu-0 films with onset of superconductivity at 105 K and zero resistance at 90.2 K were obtained, by Chaudhari et a1 [l], by electron beam evaporation from Y, Ba and Cu metallic sources on SrTiO, substrates; these films had critical current densities of 106A cm-2 at 4.2 K [l]. Similar values for the critical current and T, values of 93-90 K (90%-10%) for the resistive transition have been found by Oh et a1 [2], also using an electron beam evaporation technique.…”

Depairing current density through a low-angle grain boundary in a superconducting film

“…24,25 However, the trend of the depairing current density is qualitative agreement with the experimental results for J c . As mentioned previously, our model is invalid for high-angle grain boundaries.…”

Measurements on thin-film high-Tc superconductors

“…formula is indeed valid for high-r^ films was given in [23]. In fact, like many other laboratories, we have found that the better the film quality, the higher its critical current density.…”