Change of antiferromagnetic structure near a quantum critical point inCeRh1−xCoxIn5

Abstract

The elastic neutron-scattering experiments were carried out on the solid solutions ${\text{CeRh}}_{1\ensuremath{-}x}{\text{Co}}_{x}{\text{In}}_{5}$ to clarify the nature of the antiferromagnetic (AF) state in the vicinity of the quantum critical point: ${x}_{c}\ensuremath{\sim}0.8$. The incommensurate AF order with the wave vector of ${q}_{h}=(1/2,1/2,\ensuremath{\sim}0.3)$ observed in pure ${\text{CeRhIn}}_{5}$ is weakly suppressed upon doping with Co, and a commensurate ${q}_{c}=(1/2,1/2,1/2)$ and an incommensurate ${q}_{1}=(1/2,1/2,\ensuremath{\sim}0.42)$ AF structures evolve at intermediate Co concentrations. The AF orders with ${q}_{c}$ and ${q}_{1}$ are enhanced at $x=0.7$, and furthermore, the ${q}_{h}$ AF order vanishes. These results suggest that the AF correlations with the ${q}_{c}$ and ${q}_{1}$ modulations are significantly enhanced in the intermediate $x$ range, and may be connected with the evolution of the superconductivity observed above $x\ensuremath{\sim}0.3$.