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

Single crystals of Ba0.6K0.4Fe2As2 with excellent quality have been successfully grown without fluxing agent through a simple one-step method for the first time. X-ray diffraction patterns demonstrate that the samples have high crystalline quality and c-axis orientation. The onset transition temperature is up to 38 K with the zero resistivity temperature about 36.7 K. Both the R-T and M-T data show a very sharp superconducting transition with transition width 0.4 K. We also found that the samples possess very large current carrying ability and high upper critical fields, 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.