  Low temperature magnetic properties of Cd-doped Ce2MIn8 (M = 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
TN = 2.8 K (x = 0) to TN = 4.8 K (x = 0.21) for Ce2RhIn8-xCdx and induces long
range AFM ordering with TN = 3.8 K (x = 0.21) for Ce2IrIn8-xCdx. Additionally,
X-ray and neutron magnetic scattering studies showed that Cd-doped samples
present below TN a commensurate antiferromagnetic structure with a propagation
vector (1/2,1/2,0). 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 Ce3+ ground state single ion anisotropy modifying the crystalline
electrical field (CEF) parameters at the Ce3+ 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 CeMIn5 (M = Co, Rh and Ir) confirms the
claims that the Cd-doping induced electronic tuning is the main effect favoring
AFM ordering in these compounds.
