Direct Observation of Local Shielding Currents in Superconducting Thin Films under Low Magnetic Field by Scanning Superconducting Quantum Interference Device Microscopy

We have observed local shielding current flows in oxide superconducting thin films under low magnetic field by scanning probe microscopy using a superconducting quantum interference device (SQUID). The strength and direction of current flow were characterized simultaneously and directly by observing magnetic signals around artificial holes. This method allows us to map the current flow without reverse Fourier transform. In this paper, experimental data and analyses of the current flows in oxide superconducting thin films up to 50 μT are shown. Furthermore, results of calculation based on a very simple model are also presented. The possibility of using scanning SQUID microscopy to characterize current flow is presented.