Simple One-Step Synthesis and Superconducting Properties of SmFeAsO1–xFx

The recent discovery of superconductivity in REFeAsO (RE, rare-earth metal) has generated enormous interest because these materials are the first non-copper oxide superconductors with critical temperatures Tc exceeding 50 K as well as upper critical fields well above 100 T. However, for these new superconductors, very complicated synthesis routes, such as the complex two-step synthesis or high-pressure sintering, are required. Furthermore, there is the toxicity and volatility of arsenic to consider, sometimes a sealed quartz tube of arsenic exploded during annealing. We present a new method for producing high-temperature SmFeAsO1–xFx superconductors by using a one-step sintering process. Superconducting transition with the onset temperature of 54.6 K and high critical fields Hc2(0) ≥ 200 T were confirmed in SmFeAsO0.7F0.3. At 5 K and at self field, critical current densities Jc estimated from the magnetization hysteresis using the whole sample size and the average particle size have reached 8.5 × 103 and 1.2 × 106 A/cm2, respectively. Moreover, Jc exhibited a very weak dependence on magnetic field. This simple and safe one-step synthesis technique should be effective in other rare earth derivatives of iron-based superconductors. (condensed matter: electronicstructure, electrical, magnetic, and opticalproperties)