Low-temperature magnetic properties of Cd-doped ${\text{Ce}}_{2}M{\text{In}}_8$ ($M=\text{Rh}$ and Ir) single crystals are investigated. Experiments of temperature-dependent magnetic-susceptibility, heat-capacity, and electrical-resistivity measurements revealed that Cd doping enhances the antiferromagnetic (AFM) ordering temperature from $T_N=2.8\text{K}$ $\left(x=0\right)$ to $T_N=4.8\text{K}$ $\left(x=0.21\right)$ for ${\text{Ce}}_2{\text{RhIn}}_{8-x}{\text{Cd}}_x$ and induces long-range AFM ordering with $T_N=3.8\text{K}$ $\left(x=0.21\right)$ for ${\text{Ce}}_2{\text{IrIn}}_{8-x}{\text{Cd}}_x$. Additionally, x-ray and neutron magnetic scattering studies showed that Cd-doped samples present below $T_N$ a commensurate antiferromagnetic structure with a propagation vector $\vec{\epsilon }=\left(\frac{1}{2},\frac{1}{2},0\right)$. The resolved magnetic structures for both compounds indicate that the Cd doping tends to rotate the direction of the ordered magnetic moments toward the $ab$ plane. This result suggests that the Cd doping affects the ${\text{Ce}}^{3+}$ ground-state single-ion anisotropy modifying the crystalline electrical field (CEF) parameters at the ${\text{Ce}}^{3+}$ site. Indications of CEF evolution induced by Cd doping were also found in the electrical-resistivity measurements. Comparisons between our results and the general effects of Cd doping on the related compounds $\text{Ce}M{\text{In}}_5$ ($M=\text{Co}$, Rh, and Ir) confirms the claims that the Cd doping induced electronic tuning is the main effect favoring AFM ordering in these compounds.

• Received 22 December 2009

DOI:https://doi.org/10.1103/PhysRevB.81.245115