Phase separation and suppression of the structural and magnetic transitions in superconducting doped iron tellurides, Fe(1+x)Te(1-y)S(y).
Phase separation and suppression of the structural and magnetic transitions in superconducting doped iron tellurides, Fe(1+x)Te(1-y)S(y).
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DOI：
10.1021/ja105279p
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发表时间：
2010-08
影响因子：
15
通讯作者：
P. Zajdel;P. Hsieh;E. Rodriguez;N. Butch;J. Magill;J. Paglione;P. Zavalij;M. Suchomel;M. Green-M.-Gr
中科院分区：
文献类型：
--
作者：
P. Zajdel;P. Hsieh;E. Rodriguez;N. Butch;J. Magill;J. Paglione;P. Zavalij;M. Suchomel;M. Green-M.-Gr
在0 ≤ y ≤ 0.15的范围内，形成了名义成分为Fe（（1.15））Te（（1-）y）S（y）的铁硫系超导体的单晶和粉末样品。它们以四方反PbO结构结晶，该结构由边缘共享的Fe（Te，S）（4）四面体层组成。当y = 0时，Fe（1+x）Te（x ≤ 0.12（1））是非超导的，在2065 K时经历了四斜晶系（P4/nmm）到单斜晶系（P2（1）/m）的结构转变，并在q =（0.5 0 0.5）时出现了相应的反铁磁序。结果表明，当0 ≤ y ≤ 0.015时，Fe（1+x）Te（1-y）S（y）在低温下转变为正交晶系（Pmmn），在q =（0.5-δ 00.5）处，磁散射被大大抑制，磁散射变为无公度，并具有短程磁关联，与二维Warren峰形很好地拟合.在高得多的S浓度下（y ≥ 0.075），结构和磁性转变都受到抑制，在9 K时观察到超导转变。在这两个组成区域之间，存在相分离区域（0.025 ≤ y ≤ 0.05），其中低温中子衍射数据最好用包含四方相和正交相的模型来精确。发现硫量的增加与间隙铁x的减少有关。组成为Fe（（1.123（5））Te（（0.948（4）））S（（0.052（4）））的单晶的微探针分析证实了晶体内存在组成变化，从而使观察到的相分离合理化。
Single crystal and powder samples of the series of iron chalcogenide superconductors with nominal composition, Fe((1.15))Te((1-)y)S(y), are found to form for 0 ≤ y ≤ 0.15. They crystallize in the tetragonal anti-PbO structure, which is composed of layers of edge-shared Fe(Te, S)(4) tetrahedra. For y = 0, Fe(1+x)Te (x ≈ 0.12(1)) is nonsuperconducting and undergoes a tetragonal (P4/nmm) to monoclinic (P2(1)/m) structural transition at ∼65 K, associated with the onset of commensurate antiferromagnetic order at q = (0.5 0 0.5). We show that on sulfur substitution, Fe(1+x)Te(1-y)S(y) becomes orthorhombic (Pmmn) at low temperature for 0 ≤ y ≤ 0.015, where the greatly suppressed magnetic scattering is now incommensurate at q = (0.5-δ 0 0.5) and possesses short ranged magnetic correlations that are well fitted with a two-dimensional Warren peak shape. At much higher concentrations of S (y ≥ 0.075), there is suppression of both the structural and magnetic transitions and a superconducting transition at 9 K is observed. Between these two composition regimes, there exists a region of phase separation (0.025 ≤ y ≤ 0.05), where the low temperature neutron diffraction data is best refined with a model containing both the tetragonal and orthorhombic phases. The increase in the amount of sulfur is found to be associated with a reduction in interstitial iron, x. Microprobe analysis of a single crystal of composition Fe((1.123(5)))Te((0.948(4)))S((0.052(4))) confirms the presence of compositional variation within the crystals, rationalizing the observed phase separation.