One-step method to grow Ba0.6K0.4Fe2As2 single crystals without fluxing agent

Single crystals of Ba0.6K0.4Fe2As2 have been successfully grown without using any fluxing agent through a simple one-step method. X-ray diffraction patterns demonstrate that they have high crystalline quality and c-axis orientation. The onset transition temperature is up to 38 K, while the zero resistivity temperature reaches 36.7 K. Both the R-T and M-T data show very sharp superconducting transitions and the transition width is about 0.4 K. We also found that the samples possess very large current carrying ability and high upper critical field, indicating potential applications requiring very high field. The above simple and safe one-step technique of single crystal growth can be effective in other systems of Fe-based superconductors.