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Specific heat and disorder in the mixed state of non-magnetic borocarbides

D. Lipp·M. Schneider·A. Gladun·S. -L. Drechsler·J. Freudenberger·G. Fuchs·K. Nenkov·K. -H. Müller·T. Cichorek·P. Gegenwart
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Abstract

The temperature and magnetic field dependence of the specific heat cp(T,H) in the superconducting mixed state as well as the upper critical field Hc2(T) have been measured for polycrystalline Y_xLu_{1-x}Ni_2B_2C and Y(Ni_{1-y}Pt_y)_2B_2C samples. The linear-in-T electronic specific heat contribution gamma(H)T exhibits significant deviations from the usual linear-in-H law for all x and y the transition metal site (T) resulting in a disorder dependent negative curvature of gamma(H). The deviations from that linear behaviour of our unsubstituted samples are the largest reported so far for any superconductor. The H_c2(T) data point to the quasi-clean limit for (Y,Lu)-substitutions and to a transition to the quasi-dirty limit for (Ni,Pt)-substitutions. The gamma(H) dependence is discussed in the unitary d-wave as well as in the quasi-clean s-wave limits. From a consideration of gamma(H) data only, d-wave pairing cannot be ruled out.

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D. Lipp, M. Schneider, A. Gladun, S. -L. Drechsler, J. Freudenberger, G. Fuchs, K. Nenkov, K. -H. Müller, T. Cichorek, P. Gegenwart. 2001-04-26. Specific heat and disorder in the mixed state of non-magnetic borocarbides. https://doi.org/10.1209/epl%2Fi2002-00392-7

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