NMR Studies of Sn clathrates

ORAL

Abstract

Clathrates are materials with an open cage structure. Because of the low thermal conductivities these materials may be good choices for thermoelectric applications and energy saving devices. Thus they have become important materials for current study. We report $^{71}$Ga NMR experiments on Ba$_{8}$Ga$_{16}$Sn$_{30}$ clathrates, which have particularly low thermal conductivities We will compare different properties of the two types of Ba$_{8}$Ga$_{16}$Sn$_{30}$ clathrates, type-I and type-VIII, which are different in structure. The NMR lineshapes and relaxation times were measured in temperatures between 295K and 4.2K. For a type-I sample, we observe several different peaks with an unexpectedly large range of Knight shift. Also we observe large changes for the relaxation times at low temperature which are not consistent with the Korringa law, the normal behavior for NMR due to conduction electrons. These results are different from what we observe in other clathrates. Thus we tentatively assign these results to rattling type atomic motion, and will compare the data to models for relaxation due to such motion. This research is supported by the Robert A. Welch Foundation.

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Authors

  • Xiang Zheng

    Department of Physics, Texas A\&M University

  • Mikhail Zhernenkov

    Angelo State University Department of Physics, Department of Electrical and Computer Engineering, Texas Tech University, The University of Texas at San Antonio, Univeristy of Central Florida-College of Optics and Photonics, BAE Systems, University of Alberta Department of Physics, Istanbul University Department of Physics, Texas Tech University Department of Physics, Istanbul University, Beyazit, University of Alberta, Edmonton, UTD, TAMS at UNT, Department of Mechanical Engineering, The University of Texas at El Paso, El Paso, TX 79968, College of Nanoscale Science and Engineering, University at Albany, Dept. of Physics, University of New Orleans, University of Texas at Arlington, Prairie View A\&M University, Chemistry, UTSA, Sciprint.org, Texas Tech University Department of Electrical and Computer Engineering, Texas State University, Punjab U, Dept. of Mechanical Engineering, University of Texas, Dept. of Physics, Texas State University, Department of Physics, University of Texas at Dallas, Richardson TX 75080, Department of Physics, Texas A\&M University, College Station, Texas 77843-4242, Department of Physics, University of California, San Diego, California 92093, Universidade Federal Fluminense, Volta Redonda, RJ, Brazil, Universidade de Sao Paulo, Sao Paulo, SP, Brazil, Department of Physics, Texas A\&M University, University of Colorado at Colorado Springs, Federal University of Rio Grande do Norte, University of Texas Arlington, Harvard-Smithsonian Center for Astrophysics, Max Plank Institute, Dresden, Germany, Education Consultant, APS, The University of Texas M. D. Anderson Cancer Center, Department of Physics, Texas A\&M University, College Station, TX 77843, LANSCE, Los Alamos National Laboratory

  • Mikhail Zhernenkov

    Angelo State University Department of Physics, Department of Electrical and Computer Engineering, Texas Tech University, The University of Texas at San Antonio, Univeristy of Central Florida-College of Optics and Photonics, BAE Systems, University of Alberta Department of Physics, Istanbul University Department of Physics, Texas Tech University Department of Physics, Istanbul University, Beyazit, University of Alberta, Edmonton, UTD, TAMS at UNT, Department of Mechanical Engineering, The University of Texas at El Paso, El Paso, TX 79968, College of Nanoscale Science and Engineering, University at Albany, Dept. of Physics, University of New Orleans, University of Texas at Arlington, Prairie View A\&M University, Chemistry, UTSA, Sciprint.org, Texas Tech University Department of Electrical and Computer Engineering, Texas State University, Punjab U, Dept. of Mechanical Engineering, University of Texas, Dept. of Physics, Texas State University, Department of Physics, University of Texas at Dallas, Richardson TX 75080, Department of Physics, Texas A\&M University, College Station, Texas 77843-4242, Department of Physics, University of California, San Diego, California 92093, Universidade Federal Fluminense, Volta Redonda, RJ, Brazil, Universidade de Sao Paulo, Sao Paulo, SP, Brazil, Department of Physics, Texas A\&M University, University of Colorado at Colorado Springs, Federal University of Rio Grande do Norte, University of Texas Arlington, Harvard-Smithsonian Center for Astrophysics, Max Plank Institute, Dresden, Germany, Education Consultant, APS, The University of Texas M. D. Anderson Cancer Center, Department of Physics, Texas A\&M University, College Station, TX 77843, LANSCE, Los Alamos National Laboratory