Abstract
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.
Highlights
Ce2MIn8 ͑M = Rh, Irare heavy-fermion compounds that belong to the broader family CenMIn3n+2 ͑M = Co, Rh, Ir; n = 1, 2͒ where the occurrence of unconventional superconductivityUSCin various members has provided a great opportunity to further study the relationship between magnetism, USC, and crystal structure
Higher Cd concentrations lead to a Néel temperature increase up to 4.2 K for x ϳ 0.15. This behavior in Cd-doped CeRhIn5 was suggested to be connected with an incommensurate to commensurate magnetic ordering evolution that can be induced by Cd doping in CeRhIn5.13 In Cd-doped Ce2RhIn8, we found that TN is always increasing with the Cd concentration
The Cd doping induces some changes in the CEF parameters, our results show that the direction of the ordered moment tend to rotate to the ab plane even with an increase in the TN for a Cd-doped sample, strongly suggesting that the dominant effect to raise TN in these systems is the electronic tuning induced by the Cd doping
Summary
For the heavy-fermion superconductorsHFSin this family, USC is believed to be mediated by magnetic fluctuations and their critical temperatures seem to be related to the dimensionality of their crystal structures.2–5 They are tetragonal variants of the cubic CeIn3 structure with a layer of MIn2 introduced between n blocks of CeIn3 along the c axis.. It is important and elucidative to explore the behavior for the other series in the CenMIn3n+2 ͑M = Co, Rh, Ir; n = 1 , 2͒ family and determine to what extent the same interpretation holds In this regard, to study the n = 2 member of the CenMIn3n+2 family, the Ce2MIn8 could be interesting since Cd and Sn doping are possible in the 218’s and they present an intermediate step in terms of dimensionality between the cubic CeIn3 and the 115 compounds.. Our results are compared to those found for the Ce115’s compounds and a discussion of the microscopic effect of the Cd in the GS of these systems is given
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