Dehybridizaton of the4fshell in Si-substituted CeRh3B2

The compound Ce${\mathrm{Rh}}_3$ ${\mathrm{B}}_2$ is known to order magnetically with an unusually high Curie temperature ($T_C$) of 115 K and a low saturation moment of about $0.4{\mu }_B$. We have studied the magnetic behavior of the system $\mathrm{Ce}{\mathrm{Rh}}_3{\left({\mathrm{B}}_{1-x}{\mathrm{Si}}_x\right)}_2(0\mathrm{}\le x\le 0.5)$. It is observed that on partial replacement of B by Si an anisotropic lattice expansion takes place and the magnetic moment per Ce ion increases to more than $0.8{\mu }_B$ but at the same time $T_C$ shows a remarkable decrease by an order of magnitude to 16 K for Ce${\mathrm{Rh}}_3$BSi. These results suggest that the anomalous behavior of Ce${\mathrm{Rh}}_3$ ${\mathrm{B}}_2$ arises because of the $\mathrm{Ce} 4f$ hybridization with the neighboring ligands.