Determination of the irreversibility field of YBCO thin films from pulsed high-field measurements

A thin-film YBa2Cu3O7−δ sample has been investigated with regard to its irreversibility field at low temperatures. For these investigations, the magnetic-field dependence of the electrical resistance R(H) was measured at various temperatures in pulsed magnetic fields up to 50 T. These curves show an unusual, very rapid increase of R even at low fields. We describe a method of extracting Hirr that is comparable to measurements in static magnetic fields. The irreversibility line shows the same, nearly linear behaviour at low temperatures as bulk YBa2Cu3O7−δ samples and a power-law dependence at higher temperatures. These two regions are also clearly visible in pinning force plots.