Growth and transport properties of c-axis-oriented MgB 2 thin films

Abstract

We report the growth of high quality c-axis-oriented MgB 2 thin films on Al 2O 3 substrates by using a pulsed laser deposition technique. The thin films show an onset transition temperature of 39.2 K with a sharp transition width of ∼0.15 K. X-ray diffraction patterns indicate a c-axis-oriented crystal structure perpendicular to the substrate surface. We observed high critical current densities ( J c) of ∼16 MA/cm 2 at 15 K and under self-field, which is comparable to or exceeds those of cuprate high-temperature superconductors. The extrapolation J c at 5 K was observed to be ∼40 MA/cm 2, which is the highest record for MgB 2 compounds. At a magnetic field of 5 T, the J c of ∼0.1 MA/cm 2 was detected at 15 K, suggesting that this compound is very promising candidate for the practical applications at high temperature with lower power consumption. As a possible explanation for the high current-carrying capability, the vortex-glass transition is considered.