Fabrication and characterization of SmO0.7F0.2FeAs bulk with a transition temperature of 56.5 K

The superconductivity of iron-based superconductor SmO0.7F0.2FeAs was investigated. The SmO0.7F0.2FeAs sample was prepared by the two-step solid-state reaction method. The onset resistivity transition temperature is as high as 56.5 K. X-ray diffraction (XRD) results show that the lattice parameters a and c are 0.39261 and 0.84751 nm, respectively. Furthermore, the global Jc was more than 2.3 × 105 A/cm2 at T = 10 K and H = 9 T, which was calculated by the formula of Jc = 20ΔM/[a(1  a/(3b))]. The upper critical fields, Hc2 ≈ 256 T (T = 0 K), was determined according to the Werthamer-Helfand-Hohenberg formula, indicating that the SmO0.7F0.2FeAs was a superconductor with a very promising application.