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A series of layered (Sr1-xKx)Fe2As2 compounds with nominal x = 0-0.40 are synthesized by solid state reaction method. Similar to other parent compounds of iron-based pnictide superconductors, pure SrFe2As2 shows a strong resistivity anomaly near 210 K, which was ascribed to the spin-density-wave instability. The anomaly temperature is much higher than those observed in LaOFeAs and BaFe2As2, the two prototype parent compounds with ZrCuSiAs- and ThCr2Si2-type structures. K-doping strongly suppresses this anomaly and induces superconductivity. Like in the case of K-doped BaFe2As2, sharp superconducting transitions at Tc ~ 38 K is observed. We perform the Hall coefficient measurement, and confirm that the dominant carriers are hole-type. The carrier density is enhanced by a factor of 3 in comparison to F-doped LaOFeAs superconductor. 相似文献
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We report on a comparative optical investigation on EuFe2As2 and LaFeAsO polycrystalline samples. The spin-density wave (SDW) partial gap is observed for both compounds. The gap-like absorption peaks in the real part of conductivity for EuFe2As2 and LaFeAsO scale with their respective T SDW. Most remarkably, the study reveals a substantial difference in optical reflectance spectra for the two prototype compounds of 122 and 1111 systems: EuFe2As2 shows a much higher reflectivity with fewer phonon modes than that of LaFeAsO. This yields optical evidence for much stronger anisotropy between ab-plane and c-axis in 1111-type compounds. 相似文献
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