Superconductivity in fluoride-arsenide Sr1-xLaxFeAsF compoundsXiyu Zhu, Fei Han, Peng Cheng, Gang Mu, Bing Shen, Lei Fang and Hai-Hu Wen
National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences - P. O. Box 603, Beijing 100190, PRC
received 17 November 2008; accepted in final form 8 December 2008; published January 2009
published online 20 January 2009
By using a two-step solid-state reaction method, we successfully fabricated the new family of fluoride-arsenide AeFeAsF compounds (Ae = alkaline-earth elements, Sr, Eu and Ca) with the ZrCuSiAs structure and with the new building block AeF instead of the REO (both the formal charge of the AeF Layer and the REO layer are “+1"). The undoped parent phase has a Spin-Density-Wave–like transition at about 173 K for SrFeAsF, 118 K for CaFeAsF and 153 K for EuFeAsF. By doping electrons into the system the resistivity anomaly associated with this SDW transition is suppressed and superconductivity appears at 29.5 K (with the criterion of 90% of the normal-state resistivity) in the fluoride-arsenide Sr1-xLaxFeAsF (x = 0.4). Our discovery here suggests that other new superconductors may be obtained if one uses different rare-earth elements to substitute the alkaline-earth elements in AeFeAsF.
74.10.+v - Occurrence, potential candidates.
74.70.Dd - Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.).
74.20.Mn - Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
© EPLA 2009