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arXiv 0901.2728cond-mat.supr-concond-mat.mtrl-sci
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铁磷族化合物:单晶生长及掺杂对结构、输运和磁性的影响

Iron pnictides: Single crystal growth and effect of doping on structural, transport and magnetic properties

G. L. Sun, D. L. Sun, M. Konuma, P. Popovich, A. Boris, J. B. Peng, K. -Y. Choi, P. Lemmens, C. T. Lin

摘要:

我们证明了大的,独立的铁磷属元素化物单晶的制备与尺寸高达20 × 10 × 1毫米3,在氩气气氛下使用氧化锆坩埚中的溶剂。研究了钾掺杂对化合物结构和超导性能的影响。在BaFe_2As_2单晶中,由于Sn溶剂的生长,自熔性的自旋密度波(SDW)异常从Ts ~138 K移动到Ts ~85 K。我们表现出直接的证据,纳入锡的Fe网站。电阻率数据表明,Ba_(0.68)K_(0.32)Fe_(2As)_2单晶具有一个陡峭的超导转变温度Tc~38.5 K。磁化率数据证实了近100%的屏蔽分数和超导体的整体性质的单晶。Sr_(0.85)K_(0.15)Fe_(2As)_2单晶在Tc~25 K发生了一个急剧的相变。有直接的证据表明,在低掺杂制度的Sr 1-xKxFe 2As 2单晶的SDW和超导性的共存。掺杂效应以及两个序参量共存的结构影响进行了讨论。

英文摘要:

We demonstrate the preparation of large, free standing iron pnictide single crystals with a size up to 20 x 10 x 1 mm3 using solvents in zirconia crucibles under argon atmosphere. Transport and magnetic properties are investigated to study the effect of potassium doping on the structural and superconducting property of the compounds. The spin density wave (SDW) anomaly at Ts ~138 K in BaFe2As2 single crystals from self-flux shifts to Ts ~85 K due to Sn solvent growth. We show direct evidence for an incorporation of Sn on the Fe site. The electrical resistivity data show a sharp superconducting transition temperature Tc~38.5 K for the single crystal of Ba0.68K0.32Fe2As2. A nearly 100% shielding fraction and bulk nature of the superconductivity for the single crystal were confirmed by magnetic susceptibility data. A sharp transition Tc~25 K occurred for the single crystal of Sr0.85K0.15Fe2As2. There is direct evidence for a coexistence of the SDW and superconductivity in the low doping regime of Sr1-xKxFe2As2 single crystals. Structural implications of the doping effects as well as the coexistence of the two order parameters are discussed.

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