Thermal transport of the single-crystal rare-earth nickel borocarbides RNi2B2C
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The quaternary intermetallic rare-earth nickel borocarbides RNi2B2C are a family of compounds that show magnetic behavior, superconducting behavior, and/or both. Thermal transport measurements reveal both electron and phonon scattering mechanisms, and can provide information on the interplay of these two long-range phenomena. In general the thermal conductivity kappa is dominated by electrons, and the high temperature thermal conductivity is approximately linear in temperature and anomalous. For R=Tm, Ho, and Dy the low-temperature thermal conductivity exhibits a marked loss of scattering at the antiferromagnetic ordering temperature T-N. Magnon heat conduction is suggested for R=Tm. The kappa data for R=Ho lends evidence for gapless superconductivity in this material above T-N. Unlike the case for the non-magnetic superconductors in the family, R=Y and Lu, a phonon peak in the thermal conductivity below T-c is not observed down to T=1.4 K for the magnetic superconductors. Single-crystal quality seems to have a strong effect on kappa. The electron-phonon interaction appears to weaken as one progresses from R=Lu to R=Gd. The resistivity data shows the loss of scattering at T-N for R=Dy, Tb, and Gd; and the thermoelectric power for all three of these materials exhibits an enhancement below T-N.