paper

c-axis magnetotransport in CeCoIn

arXiv:cond-mat/0503721 · doi:10.1103/PhysRevB.72.184506

Abstract

We present the results of out-of-plane electrical transport measurements on the heavy fermion superconductor CeCoIn at temperatures from 40 mK to 400 K and in magnetic field up to 9 T. For 10 K transport measurements show that the zero-field resistivity changes linearly with temperature and extrapolates nearly to zero at 0 K, indicative of non-Fermi-liquid (nFL) behavior associated with a quantum critical point (QCP). The longitudinal magnetoresistance (LMR) of CeCoIn for fields applied parallel to the c-axis is negative and scales as between 50 and 100 K, revealing the presence of a single-impurity Kondo energy scale K. Beginning at 16 K a small positive LMR feature is evident for fields less than 3 tesla that grows in magnitude with decreasing temperature. For higher fields the LMR is negative and increases in magnitude with decreasing temperature. This sizable negative magnetoresistance scales as from 2.6 K to roughly 8 K, and it arises from an extrapolated residual resistivity that becomes negative and grows quadratically with field in the nFL temperature regime. Applying a magnetic field along the c-axis with B B restores Fermi-liquid behavior in at less than 130 mK. Analysis of the resistivity coefficient's field-dependence suggests that the QCP in CeCoIn is located \emph{below} the upper critical field, inside the superconducting phase. These data indicate that while high- c-axis transport of CeCoIn exhibits features typical for a heavy fermion system, low- transport is governed both by spin fluctuations associated with the QCP and Kondo interactions that are influenced by the underlying complex electronic structure intrinsic to the anisotropic CeCoIn crystal structure.

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