Upper critical field study of CH$_{4}$ HPCVD carbon-doped MgB$_{2}$

ORAL

Abstract

The $H_{c2}(T)$ of a set of four carbon-doped MgB$_{2}$ films grown on both SiC and Al$_{2}$O$_{3 }$substrates by HPCVD from methane CH$_{4}$ at flow rates from 7 to 10 sccm were measured in fields up to 65T. Compared to early metalorganic C sources which generated high $H_{c2}(0)$, these films have much lower resistivities and higher connectivities. The curvature of $H_{c2}(T)$ derived from low current four point magnetoresistance shows upturn at low temperatures, which is consistent with the dominance of \textit{$\pi $}-band scattering in the theory of dirty two-gap superconductivity. $H_{c2}^{\vert }$(0) $>$ 60T is close to the paramagnetic limit of $\sim $ 66T for the 10 sccm film on SiC, though still a little lower than for the previously used metalorganic (C$_{6}$H$_{7})_{2}$Mg. Differences in the $H_{c2}(T)$ behavior between films grown on the two substrates are attributed to variations in strain fields produced by the substrate coupled to the film at growth.

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Authors

  • F. Hunte

    • NHMFL-Florida State University

  • J. Jaroszynski

    • National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
    • NHMFL
    • NHMFL-Florida State University

  • Alex Gurevich

    • NHMFL
    • Florida State University
    • NHMFL-Florida State University
    • National High Magnetic Field Laboratory

  • David Larbelestier

    • National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
    • Florida State University
    • NHMFL-Florida State University

  • Ye Zhu

    • University of Wisconsin, Madison
    • Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706

  • Paul Voyles

    • University of Wisconsin, Madison
    • Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706

  • X.X. Xi

    • Pennsylvania State University
    • Department of Physics, Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802
    • The Pennsylvania State University
    • Department of Physics and Department of Materials Science and Engineering, Penn State University, University Park, PA 16802

  • K. Chen

    • The Pennsylvania State University

  • S. Baily

    • NHMFL-Los Alamos National Laboratory

  • Fedor Balakirev

    • National High Magnetic Field Laboratory
    • NHMFL
    • NHMFL-Los Alamos National Laboratory
    • Los Alamos National Laboratory

  • C.G. Zhuang

    • Peking University

  • S. Meng

    • Peking University

  • C. Y. Zhang

    • Peking University

  • Q.R. Feng

    • Peking University

  • Z.Z. Gan

    • Peking University