Enhancement at low temperatures of the critical current density for Au-coated MgB2 thin films

We measured the superconducting critical current densities (J(c)) from the magnetization hysteresis (M-H) loop for Au-coated MgB2 thin films. The purpose of this experiment was to determine whether the vortex avalanche phenomenon which suppresses the J(c) for low temperature (T<15 K) and low field (Hless than or equal to1000 Oe) could be cured by gold deposition. This avalanche, called flux noise, has been a headache in applications of MgB2 thin films. Fortunately, the flux noise in the M-H loop is suppressed with increasing Au-film thickness and finally disappears when the thickness of the gold becomes 2.55 mum. We found a way to remove one obstacle for applications of MgB2 thin films as an superconducting device. (C) 2004 American Institute of Physics.