Eu0.5La0.5FBiS2-xSex is a new BiS2-based superconductor system. In Eu0.5La0.5FBiS2-xSex, electron carriers are doped to the BiS2 layer by the substitution of Eu by La. Bulk superconductivity in this system is induced by increasing the in-plane chemical pressure, which is controlled by the Se concentration (x). In this study, we have analysed the crystal structure of Eu0.5La0.5FBiS2-xSex using synchrotron powder diffraction and the Rietveld refinement. The precise determination of the structural parameters and thermal factors suggest that the emergence of bulk superconductivity in Eu0.5La0.5FBiS2-xSex is achieved by the enhanced in-plane chemical pressure and the decrease in in-plane disorder.
Pressure dependence of the low- temperature crystal structure and phase transition behaviour of CaFeAsF and SrFeAsF: A synchrotron x-ray diffraction study
First-order structural transition in the magnetically ordered phase of Fe1.13Te
比热,电阻率,磁化率,线性热膨胀(LTE),和高分辨率同步X射线粉末衍射研究的单晶Fe 1 +yTe(0.06 < y < 0.15)揭示了分裂的一个单一的,一级跃迁y < 0.11 into two transitions for y >0.12。最引人注目的是,对相同样品Fe_(1.13)Te的所有测量一致表明,冷却时,T_N处的磁转变先于较低温度T_s处的一级结构转变。结构转变又与磁结构特征的变化相一致。沿晶体学c轴的LTE测量显示,由于磁有序导致的晶格收缩,在T_N附近出现较小的变形,而在T_s处出现更大的变化。粉末X射线衍射表明,在低于T_s时,晶格对称性发生变化。这种行为与铁磷属元素化物中发生相变的顺序形成鲜明对比。
The preparation and phase diagrams of (${^{7}}$Li${_{1-x}}$Fe${_{x}}$OD)FeSe and (Li${_{1-x}}$Fe${_{x}}$OH)FeSe superconductors
本文报道了(${^{7}}$ Li ${_{1-x}}$ Fe ${_{x}}$ OD)FeSe超导体系的相图,并与(Li ${_{1-x}}$ Fe ${_{x}}$ OH)FeSe单晶和粉末的相图进行了对比。通过水热法制备样品,并通过实验室和同步辐射X射线衍射,高分辨率中子粉末衍射(NPD)和高强度NPD进行表征。我们发现的四方性的晶胞参数和临界温度,$T_{c}$,这是指示的电荷掺杂的晶格和铁空位的形成在FeSe层的影响之间的相关性。我们观察到用D取代H时,对最大$T_{c}$没有明显的同位素效应。NPD测量明确地排除了在低于120 K的非超导(Li ${_{1-x}}$ Fe ${_{x}}$ OD)FeSe样品中的反铁磁有序,这在非超导(Li ${_{1-x}}$ Fe ${_{x}}$ OH)FeSe中已经报道。在(Li ${_{1-x}}$ Fe ${_{x}}$ OH)FeSe样品中观察到的反铁磁转变的一个可能的解释是在它们的制备过程中杂质的形成,例如Fe ${_{3}}$ O ${_{4}}$和LixFeO 2,它们在120 K附近表现出被称为Verwey转变的电荷有序转变。发现这些氧化物杂质的浓度取决于氢氧化锂试剂的浓度和在合成期间作为溶剂的H ${_{2}}$ O与D ${_{2}}$ O的使用。我们还描述了反应条件,导致我们的一些超导样品表现出低于$T_{c…