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