Growth of big single crystals of a new magnetic superconducting double perovskite Ba₂PrRu_1-xCu_xO₆

Single crystals of Ba₂PrRu_1-xCu_xO ₆ with x=0 to 0.2, have been grown from high temperature solutions of a mixture of PbO-PbF₂ in the temperature range 1100-1200°C. Thin crystals with mostly a hexagonal and triangular plate like habit measuring up to 1-2mm across and 0.1-0.2 mm thick were obtained. The size, quality and morphology of the crystals were improved by varying the solution volume as well as additives like B₂O₃. Large crystals measuring up to 3mm across and 0.3 to 0.5 mm thick were obtained with 5-7 wt% solute concentration and 0.5-1 wt% of B₂O₃. The ZFC curves exhibit a spin glass like behavior with x = 0 and a superconducting transition at 8 to 11 K depending on x - 0.05 to 0.1. The transition was also influenced by the growth temperature and post growth annealing. Powder x-ray diffraction, EDS and Raman spectroscopic measurements confirm the presence of Cu in the crystals.