Iyo Akira, Hase Izumi, Kawashima Kenji, Ishida Shigeyuki, Kito Hijiri, Takeshita Nao, Oka Kunihiko, Fujihisa Hiroshi, Gotoh Yoshito, Yoshida Yoshiyuki, Eisaki Hiroshi
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.
Inorg Chem. 2017 Jul 17;56(14):8590-8595. doi: 10.1021/acs.inorgchem.7b01446. Epub 2017 Jun 28.
We have succeeded in crystallizing a new strontium digermanide (SrGe) with the ThSi-type structure (tetragonal SrGe), which is theoretically predicted to compete with the EuGe-type one (trigonal SrGe) under pressure. The tetragonal SrGe appeared as a metastable phase in samples at approximately 900 °C under a pressure of 2 GPa. X-ray diffraction studies show that the tetragonal SrGe is formed by the reaction between trigonal SrGe and excess Sr. The composition of the tetragonal SrGe was analyzed to be SrGe. Lattice parameters for the tetragonal SrGe are determined to be a = 4.559(4) Å and c = 14.42(1) Å. The tetragonal SrGe shows metallic resistivity behavior and exhibits superconductivity with a critical temperature (T) of 7.3 K, which is the highest among compounds with the ThSi-type structure. Superconducting properties of the tetragonal SrGe, such as the upper critical field, and the effect of pressure on T, are presented and superconductivity is discussed on the basis of electronic band structure calculations.
我们成功地使一种具有ThSi型结构（四方SrGe）的新型二锗化锶（SrGe）结晶，理论预测该结构在压力下会与EuGe型结构（三角SrGe）相互竞争。四方SrGe在2 GPa压力下约900 °C的样品中以亚稳相出现。X射线衍射研究表明，四方SrGe是由三角SrGe与过量Sr之间的反应形成的。经分析，四方SrGe的组成为SrGe。确定四方SrGe的晶格参数为a = 4.559(4) Å和c = 14.42(1) Å。四方SrGe表现出金属电阻率行为，并在7.3 K的临界温度（T）下呈现超导性，这在具有ThSi型结构的化合物中是最高的。本文介绍了四方SrGe的超导特性，如高临界场以及压力对T的影响，并基于电子能带结构计算对超导性进行了讨论。
