One-component description of magnetic excitations in the heavy-fermion compoundCeIrIn5

We report an $^{115}\text{I}\text{n}$ NMR study of a single-crystal sample of the heavy-fermion compound ${\text{CeIrIn}}_{5}$. The observed nonlinear variation in Knight shift with static susceptibility is consistent with the two-fluid model of Nakatsuji et al. However, our results can also be understood in terms of a $T$-dependent hyperfine coupling, which accounts for the spin-lattice relaxation data naturally on the basis of a one-component dynamical susceptibility. In addition, the observed $T$ dependence of the hyperfine coupling is scaled to a density of states given by dynamical mean-field theory.