High-Tc superconductivity induced by doping rare-earth elements into CaFeAsFPeng Cheng, Bing Shen, Gang Mu, Xiyu Zhu, Fei Han, Bin Zeng 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 10 December 2008; accepted in final form 23 February 2009; published March 2009
published online 1 April 2009
We have successfully synthesized the fluoride-arsenide compounds Ca1-xRExFeAsF (RE = Nd, Pr; x = 0,0.6). The X-ray powder diffraction confirmed that the main phases of our samples are Ca1-xRExFeAsF with the ZrCuSiAs structure. By measuring resistivity, superconductivity was observed at 56 K in Nd-doped and 52 K in Pr-doped samples with x=0.6. Bulk superconductivity was also proved by the DC magnetization measurements in both samples. Hall effect measurements revealed hole-like charge carriers in the parent compound CaFeAsF with a clear resistivity anomaly below 118 K, while the Hall coefficient RH in the normal state is negative for the superconducting samples Ca0.4Nd0.6FeAsF and Ca0.4Pr0.6FeAsF. This indicates that the rare-earth element doping introduces electrons into CaFeAsF, which induces high-temperature superconductivity.
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 models, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
© EPLA 2009