Vortex Core Size Measurements in YNi$_2$B$_2$C and TmNi$_2$B$_2$C

ORAL

Abstract

The vortex core size in type-II superconductors is typically determined from measurements of a related quantity combined with a theoretical model, with the best known example being the upper critical field and the GL-result: $\xi = \sqrt{\phi_0/2\pi H_{c2}}$. However, for many non-conventional superconductors such an approach is problematic, as for example in the case of TmNi$_2$B$_2$C and CeCoIn$_5$ where $H_{c2}$ is suppressed by coexistence with magnetism. In such instances a direct, model independent determination of the vortex core is desirable, and can be obtained by small-angle neutron scattering (SANS) measurements of the vortex lattice (VL) if a sufficient number of reflections are recorded [J. M. Densmore {\em et al.}, Phys. Rev. B {\bf 79}, 174522 (2009)]. Here we report on VL SANS studies on two members of the borocarbide superconductors, YNi$_2$B$_2$C and TmNi$_2$B$_2$C. Non-magnetic Y1221 measurements at $0.2$ and $0.5$~T show clear evidence of a vortex squeezing effect. In magnetic Tm1221 the vortex core size was found to be $\xi = 10.8$~nm, roughly a factor of two smaller than the value estimated by the measured $H_{c2}$ ($21$~nm). Supported by NSF award no. DMR-0804887 (Notre Dame) and DOE BES contract No. DE-AC02-07CH11358 (Ames).

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Authors

  • Pinaki Das

    • University of Notre Dame, IN, US
    • University of Notre Dame, IN, USA
    • University of Notre Dame

  • C. Rastovski

    • University of Notre Dame, IN, US
    • University of Notre Dame, IN, USA

  • K. Schlesinger

    • University of Notre Dame, IN, US
    • University of Notre Dame, IN, USA

  • Morten Ring Eskildsen

    • University of Notre Dame, IN, US
    • University of Notre Dame, IN, USA
    • University of Notre Dame

  • J.M. Densmore

    • Army Research Laboratory, Aberdeen, MD, USA

  • Sergey Bud'ko

    • Ames Laboratory
    • Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University
    • Iowa State University
    • Iowa State University and Ames Lab.
    • Iowa State University/Ames Lab
    • Iowa State University and Ames Laboratory US DOE
    • Ames Laboratory and Iowa State University, IA, USA
    • Ames Laboratory, Iowa State University

  • Paul Canfield

    • Ames Laboratory and Dept. of Physics and Astronomy, Iowa State University
    • Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University
    • Iowa State University
    • Iowa State University and Ames Lab.
    • Iowa State University/Ames Lab
    • Iowa State University, Ames Laboratory
    • Ames Laboratory and Iowa State University, IA, USA
    • Ames Laboratory, Ames, IA 50011, U.S.A.
    • Ames Laboratory, Iowa State University