5 research outputs found
Crystal Structure and Superconductivity of BaIr<sub>2</sub>Ge<sub>7</sub> and Ba<sub>3</sub>Ir<sub>4</sub>Ge<sub>16</sub> with Two-Dimensional Ba-Ge Networks
The Ba-Ir-Ge ternary compounds BaIr<sub>2</sub>Ge<sub>7</sub> and
Ba<sub>3</sub>Ir<sub>4</sub>Ge<sub>16</sub> 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 “edge-shared crown-shaped BaGe<sub>16</sub> polyhedra”. The layered Ba-Ge network yielded a modest
anisotropy of 1.3–1.4 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
“rattling” 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