新型结构型铁基超导体：CaAFe4As4（A = K、Rb、Cs）和 SrAFe4As4（A = Rb、Cs）。
New-Structure-Type Fe-Based Superconductors: CaAFe4As4 (A = K, Rb, Cs) and SrAFe4As4 (A = Rb, Cs).
机构信息
National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
IMRA Material R&D Co., Ltd. , 2-1 Asahi-machi, Kariya, Aichi 448-0032, Japan.
出版信息
J Am Chem Soc. 2016 Mar 16;138(10):3410-5. doi: 10.1021/jacs.5b12571. Epub 2016 Mar 4.
Fe-based superconductors have attracted research interest because of their rich structural variety, which is due to their layered crystal structures. Here we report the new-structure-type Fe-based superconductors CaAFe4As4 (A = K, Rb, Cs) and SrAFe4As4 (A = Rb, Cs), which can be regarded as hybrid phases between AeFe2As2 (Ae = Ca, Sr) and AFe2As2. Unlike solid solutions such as (Ba(1-x)K(x))Fe2As2 and (Sr(1-x)Na(x))Fe2As2, Ae and A do not occupy crystallographically equivalent sites because of the large differences between their ionic radii. Rather, the Ae and A layers are inserted alternately between the Fe2As2 layers in the c-axis direction in AeAFe4As4 (AeA1144). The ordering of the Ae and A layers causes a change in the space group from I4/mmm to P4/mmm, which is clearly apparent in powder X-ray diffraction patterns. AeA1144 is the first known structure of this type among not only Fe-based superconductors but also other materials. AeA1144 is formed as a line compound, and therefore, each AeA1144 has its own superconducting transition temperature of approximately 31-36 K.
铁基超导体因其丰富的层状晶体结构而引起了研究兴趣。在这里，我们报道了新结构类型的铁基超导体 CaAFe4As4（A=K，Rb，Cs）和 SrAFe4As4（A=Rb，Cs），它们可以被视为 AeFe2As2（Ae=Ca，Sr）和 AFe2As2 之间的混合相。与 Ba(1-x)K(x))Fe2As2 和 Sr(1-x)Na(x))Fe2As2 等固溶体不同，由于离子半径的巨大差异，Ae 和 A 并不占据晶体学等效位置。相反，Ae 和 A 层在 AeAFe4As4（AeA1144）中沿 c 轴方向交替插入 Fe2As2 层之间。Ae 和 A 层的有序排列导致空间群从 I4/mmm 转变为 P4/mmm，这在粉末 X 射线衍射图谱中明显可见。AeA1144 不仅是铁基超导体，而且是其他材料中首次发现的这种类型的结构。AeA1144 作为线化合物形成，因此，每个 AeA1144 都具有自己的超导转变温度约为 31-36 K。
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