Session H8: Focus Session: Novel Superconductors III: Mostly MgB2

8:00 AM–10:48 AM, Tuesday, March 6, 2007
Colorado Convention Center - Korbel 1C

Sponsoring Unit: DMP
Chair: Anthony Carrington, Bristol University

Abstract ID: BAPS.2007.MAR.H8.11

Abstract: H8.00011 : Superconducting and Normal State Properties of OsB$_2$*

10:24 AM–10:36 AM

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Authors:

  Yogesh Singh
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

  A. Niazi
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

  X. Zong
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

  B.J. Suh$^{\dagger}$
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

  M.W. Vannette
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

  R. Prozorov
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

  D.C. Johnston
    (Ames Lab. and Dept. Phys. and Astron., Iowa State Univ., Ames, IA 50011)

OsB$_{2}$ is a layered superhard metallic material that was found to superconduct below $T_{\rm c} = 2.1$~K.$^1$ We report the first detailed measurements of the static and dynamic magnetic susceptibilities $\chi$, electrical resistivity, heat capacity $C_{\rm p}$, penetration depth, and $^{11}$B NMR on OsB$_{2}$ to characterize its superconducting and normal state properties. The results confirm that OsB$_{2}$ is a bulk superconductor below $T_{\rm c} = 2.1$~K\@. Its properties can be described by a close to weak-coupling \emph{s}-wave BCS model with an electron-phonon coupling constant $\lambda = 0.4$--0.5, $\Delta(0)/(k_{\rm B}T_{\rm c}) \approx 1.9$, a small Ginzburg-Landau parameter $\kappa$ of order 5 or less, and a small zero-temperature critical magnetic field of roughly $500~$Oe. The $^{11}$B NMR measurements in the normal state show a nuclear spin-lattice relaxation time $T_1 = 2.1$~s at room temperature and a Korringa law with $T_1T = 610$~s$\cdot$K at lower $T$, and a correspondingly small $T$-independent Knight shift. These results indicate a small \emph{s} character of the conduction electron wave function at the B site at the Fermi level. Our results will be compared to corresponding data for MgB$_2$.\\ 1. J. K. Vandenberg et al., Mater. Res. Bull. {\bf 10}, 889 (1975).\\ $^*$Supported by the USDOE under Contract No.\ W-7405-Eng-82.\\ $\dagger$ Permanent address: Dept. Phys., The Catholic Univ. Korea.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.H8.11