Two types of multistack structures in MgB2-type superconductor caalsi

• Published in: Journal of the Physical Society of Japan 2006-04, Vol.75 (4)
• Main Authors: SAGAYAMA, Hajime, WAKABAYASHI, Yusuke, SAWA, Hiroshi, KAMIYAMA, Takashi, HOSHIKAWA, Akinori, HARJO, Stefanus, UOZATO, Kentaro, GHOSH, Ajay K, TOKUNAGA, Masashi, TAMEGAI, Tsuyoshi
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Effects of material synthesis, crystal structure, and chemical composition; Exact sciences and technology; Inorganic compounds; Metals, alloys and compounds (a15, 001c15, laves phases, chevrel phases, borocarbides, etc.); Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Superconducting materials (excluding high-tc compounds); Superconductivity; Transition temperature variations
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/jpsj.75.043713

Crystal structure analysis of an AlB2-type superconductor, CaAlSi, has been carried out using synchrotron X-rays and neutron diffraction measurements. Two different stackings along the c-axis--5-fold and 6-fold structures--with different values of Tc 6.0 and 8.2 K, respectively, are confirmed. Our results show that Al and Si atoms are ordered alternately in honeycomb layers, and Ca atoms are intercalated at regular intervals between the (Al,Si) layers in both the structures. The 5-fold and 6-fold structures are determined by the arrangement of Al and Si along the c-axis. The relation between Tc and the structure is discussed based on our structural analysis.