Nested antiferromagnetic spin fluctuations and non-Fermi-liquid behavior in electron-doped CeCo1−xNixIn5

Abstract

We investigate the electronic state of Ni-substituted ${\mathrm{CeCo}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}{\mathrm{In}}_{5}$ by nuclear quadrupole and magnetic resonance (NQR/NMR) techniques. The heavy fermion superconductivity below ${T}_{\mathrm{c}}=2.3$ K for $x=0$ is suppressed by Ni substitutions, and ${T}_{\mathrm{c}}$ reaches zero for $x=0.25$. The $^{115}\mathrm{In}$ NQR spectra for $x=0.125$ and 0.25 can be explained by simulating the electrical field gradient that is calculated for a virtual supercell with density functional theory. The spin-lattice relaxation rate $1/{T}_{1}$ indicates that Ni substitution weakens antiferromagnetic correlations that are not localized near the substituent but instead are uniform in space. The temperature ($T$) dependence of ${({T}_{1}T)}^{\ensuremath{-}1}$ for $x=0.25$ shows a maximum around ${T}_{\mathrm{g}}=2$ K and ${({T}_{1}T)}^{\ensuremath{-}1}$ decreases toward almost zero when temperature is further reduced as if a gap might be opening in the magnetic excitation spectrum; however, the magnetic specific heat and the static magnetic susceptibility evolve smoothly through ${T}_{\mathrm{g}}$ with a $\ensuremath{-}lnT$ dependence. The peculiar $T$ dependence of ${({T}_{1}T)}^{\ensuremath{-}1}$ and non-Fermi-liquid specific heat and susceptibility can be interpreted in a unified way by assuming nested antiferromagnetic spin fluctuations in a quasi-two-dimensional electronic system.