Magnetic-Field-Induced Enhancements of Nuclear Spin-Lattice Relaxation Rates in the Heavy-Fermion Superconductor CeCoIn5 Using 59Co Nuclear Magnetic Resonance

Co-59 nuclear spin-lattice relaxation has been measured for the heavy-fermion superconductor CeCoIn5 in a range of applied fields directed parallel to the c axis. An enhanced normal-state relaxation rate, observed at low temperatures and fields just above H-c2(0), is taken as a direct measure of the dynamical susceptibility and provides microscopic evidence for an antiferromagnetic instability. The results are well described using the self-consistent renormalized theory for two-dimensional antiferromagnetic spin fluctuations, and parameters obtained in the analysis are applied to previously reported specific heat and thermal expansion data with good agreement.