London-silsbee state in magnetically textured dyba2cu307_x: Filamentary percolation

A highly textured DyBa2Cu307_xsample has been grown by melting and cooling in an external magnetic field.V vs. Icharacteristics have been measured as a function oftemperature. The results are interpreted in terms of the so-called London model ofcurrent-induced destruction of superconductivity in a filamentary structure. The critical currentdeduced from theseI-Vcurves shows a linear temperature dependence which is consistent withthe so-called Silsbee state, and leads to a Silsbee critical current of ca. 380 mA atT =0, andcorresponds to a 0.5 T thermodynamic critical field. This field is in agreement with the structurededuced from microscopic observation and reveals that the percolation transition starts from afilamentary mechanism for the superconductivity destruction with increasing temperature.