Superconductivity at 23 K and Low Anisotropy in Rb-Substituted BaFe2As2 Single Crystals
Abstract
Single crystals of Ba1-xRbxFe2As2 with x=0.05-0.1 have been grown from Sn flux and are bulk superconductors with Tc up to 23 K. The crystal structure was determined by X-ray diffraction analysis, and Sn is found to be incorporated for 9% Ba, shifted by 1.1 Angstroem away from the Ba site towards the (Fe2As2)-layers. The upper critical field deduced from resistance measurements is anisotropic with slopes of 7.1(3) T/K (H || ab-plane) and 4.2(2) T/K (H || c-axis), sufficiently far below Tc. The extracted upper critical field anisotropy of 3 close to Tc, is in good agreement with the estimate from magnetic torque measurements. This indicates that the electronic properties in the doped BaFe2As2 compound are significantly more isotropic than those in the LnFeAsO family. The in-plane critical current density at 5 K exceeds 106 A/cm2, making Ba1-xRbxFe2As2 a promising candidate for technical applications.