THE FLOATING-ZONE GROWTH AND SUPERCONDUCTIVE PROPERTIES OF LA1.85SR0.15CUO4 AND ND1.85CE0.15CUO4 SINGLE-CRYSTALS

A technology was elaborated to produce large superconducting single cr ystals by use of a non-crucible floating zone melting method with ligh t radiation heating under oxygen atmosphere. Large superconducting sin gle crystals La2-xSrxCuO4 and Nd2-xCexCuO4 (x = 0.15) were obtained wi th diameters and lengths up to 7 mm and 30 mm respectively, and masses exceeding 5 g. Temperatures of the superconducting transition for La- and Nd-based single crystals were T-c = 39 and 25 K respectively, and the transition width was of the order of 1 K. Superconducting propert ies were studied by measuring resistance, AC-magnetic susceptibility a nd specific heat in magnetic fields 0 and 8 T. In the temperature depe ndence of the specific heat we observed the jumps corresponding to the superconducting transition. The content of the superconducting phase in the samples is estimated to be about 80-90%.