Superconducting properties of chill-cast YNi2B2C

Chill-cast samples of YNi2B2C show a significant depression in the critical temperature, Tc, from that observed for arc-melted buttons, presumably due to the introduction of strains and defects during the chill-casting process. Here we present a summary of measurements of the AC susceptibility and the field- and temperature-dependent resistivity and magnetisation (in fields up to 10 T) on samples in the as-cast state. A comparison of these data with those on subsequently annealed specimens indicates that annealing causes an increase in Tc, Hc1 and Hc2 as well as an (expected) decrease in the normal state resistivity. The critical current density, Jc, however, displays an anomalous increase after annealing, suggesting that the annealing process might result in the formation of a defect structure, a behaviour similar to that seen in high-Tc oxide superconductors. (orig.)