Significant enhancement of superconducting properties in the FeSe0.5Te0.5 bulks by minor Sn addition

Sn addition improves bulk superconducting properties of FeSe0.5Te0.5 with the increase of onset transition temperature and sharpens the transition width. The critical current density (Jc) of Sn-added sample is about 7x103 A cm-2 in self field and maintains a stable value of 3x102 A cm-2 even beyond 60,000 Oe at 4.3 K, much higher than that of the Sn-free one. Phase compositions and morphology characterizations indicate that minor Sn addition facilitates the formation of the superconducting phase whose composition is closer to the ideal one, and suppresses the formation of Fe7Se8 impurity and amorphous phase, which contribute to the improvement of Jc.