The role of dimensionality in the Kondo CeTX₂ family: the case of CeCd_(1-δ)Sb₂

Motivated by the presence of competing magnetic interactions in the heavy fermion family Ce$TX_2$ ($T$ = transition metal, $X$ = pnictogen), here we study the novel parent compound CeCd$_{1-\delta}$Sb$_{2}$ by combining magnetization, electrical resistivity, and heat-capacity measurements. Contrary to the antiferromagnetic (AFM) ground state observed in most members of this family, the magnetic properties of our CeCd$_{1-\delta}$Sb$_{2}$ single crystals revealed a ferromagnetic (FM) ordering at $T_{\rm c}$ = 3 K with an unusual soft behavior. By using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian, a systematic analysis of our macroscopic data was obtained. Our fits allowed us to extract a simple but very distinct CEF scheme, as compared to the AFM counterparts. As in the previously studied ferromagnet CeAgSb$_{2}$, a pure $|\pm 1/2 \rangle$ ground state is realized, hinting at a general trend within the ferromagnetic members. We propose a general scenario for the understanding of the magnetism in this family of compounds based on the subtle changes of dimensionality in the crystal structure.