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arXiv 0902.3957cond-mat.supr-concond-mat.mtrl-sci
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SrFe2-xIrxAs2在22.3 K下的超导电性

Superconductivity at 22.3 K in SrFe2-xIrxAs2

Fei Han, Xiyu Zhu, Ying Jia, Lei Fang, Peng Cheng, Huiqian Luo, Bing Shen, Hai-Hu Wen

摘要:

用5d过渡金属Ir取代SrFe_2As_2中的Fe,成功地合成了超导体SrFe_(2-x)Ir_xAs_2,其Tc = 22.3K,x = 0.5。X射线衍射分析表明,材料形成了ThCr 2Si 2型结构,空间群为I4/mmm。电阻率和直流磁化强度的温度依赖性都揭示了在22 K附近的急剧超导转变。对抗磁化信号的估计揭示了高迈斯纳屏蔽体积。有趣的是,正常状态下的电阻率表现出大致线性的行为高达300 K。在不同的磁场下的超导转变也被测量,产生的斜率-dHC 2/dT = 3.8 T/K附近的Tc。利用Werthamer-Helfand-Hohenberg(WHH)公式,得到零K时的上临界场约为58 T。通过计算SrFe_(2-x)Ir_xAs_(2-x)体系中可能掺杂的电子数,我们认为,掺Ir体系的超导电性不同于掺Co体系的超导电性,这将为铁磷属元素化物超导体的物理基础增添更多的成分。

英文摘要:

By substituting the Fe with the 5d-transition metal Ir in SrFe2As2, we have successfully synthesized the superconductor SrFe2-xIrxAs2 with Tc = 22.3 K at x = 0.5. X-ray diffraction indicates that the material has formed the ThCr2Si2-type structure with a space group I4/mmm. The temperature dependence of resistivity and dc magnetization both reveal sharp superconducting transitions at around 22 K. An estimate on the diamagnetization signal reveals a high Meissner shielding volume. Interestingly, the normal state resistivity exhibits a roughly linear behavior up to 300 K. The superconducting transitions at different magnetic fields were also measured yielding a slope of -dHc2/dT = 3.8 T/K near Tc. Using the Werthamer-Helfand-Hohenberg (WHH) formula, the upper critical field at zero K is found to be about 58 T. Counting the possible number of electrons doped into the system in SrFe2-xIrxAs2, we argue that the superconductivity in the Ir-doped system is different from the Co-doped case, which should add more ingredients to the underlying physics of the iron pnictide superconductors.

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