Crystal Structure and Superconductivity of BaIr2Ge7 and Ba3Ir4Ge16 with Two-Dimensional Ba-Ge Networks

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• 作者：Shigeyuki Ishida ; Yousuke Yanagi ; Kunihiko Oka ; Kunimitsu Kataoka ; Hiroshi Fujihisa ; Hijiri Kito ; Yoshiyuki Yoshida ; Akira Iyo ; Izumi Hase ; Yoshito Gotoh ; Hiroshi Eisaki
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：April 9, 2014
• 年：2014
• 卷：136
• 期：14
• 页码：5245-5248
• 全文大小：297K
• 年卷期：v.136,no.14(April 9, 2014)
• ISSN：1520-5126

文摘

The Ba-Ir-Ge ternary compounds BaIr₂Ge₇ and Ba₃Ir₄Ge₁₆ exhibit superconductivity (SC) at 2.5 and 5.2 K, respectively. Detailed single-crystal structural analysis revealed that these compounds share unique quasi-two-dimensional networks composed of crown-shaped Ge rings that accommodate Ba atoms at the center, referred to as 鈥渆dge-shared crown-shaped BaGe₁₆ polyhedra鈥? The layered Ba-Ge network yielded a modest anisotropy of 1.3鈥?.4 in the upper critical field, which is in good agreement with the band structure calculations. The Ba-Ge structural unit is similar to cage structures seen in various clathrates in which the anharmonic vibration of the central atoms, the so-called 鈥渞attling鈥?behavior, brings about strong-coupling SC. However, each Ba-Ge unit is relatively small compared to these materials, which likely excludes the possibility of unconventional SC.