Surface superconductivity and structural analysis of YC_(2) single crystals encapsulated in carbon nanocages

摘要

The magnetization measurements in the temperatures between 2 and 10 K and in the applied fields up to 5 T and x-ray powder diffraction measurement at 293 K for YC_(2) single crystals encapsulated in carbon nanocages are reported. The highest critical field in the magnetization curve near T_(c) is in excellent agreement with the nucleation field H_(c3) for surface superconductivity. H_(c3)(2 K), increasing with decreasing mean particle diameter, shows an effect of small-particle size of our nanocrystals. No appreciable size dependence of the Ginzburg critical region is found and suggested to be evidence of the partial suppression of surface superconductivity through the contact between YC_(2) crystals and the innermost nanocages. Structural parameters derived from the Rietveld refinement of the CaC_(2) model are consistent with those of the bulk YC_(2).