Ferromagnetic enhancement in the hexagonalCe(Rh1−xIrx)3B2system

Electrical resistivity, magnetization, and crystallographic measurements have been carried out for the pseudoternary system $\mathrm{Ce}{\left({\mathrm{Rh}}_{1-x}{\mathrm{Ir}}_x\right)}_3{\mathrm{B}}_2$. A single-phase hexagonal Ce${\mathrm{Co}}_3$ ${\mathrm{B}}_2$-type structure persists from $x=0.0\mathrm{}$ up to $x<\mathrm{}0.75\mathrm{}$, through a narrow two-phase region at higher iridium concentration, and transforms to a monoclinic Er${\mathrm{Ir}}_3$ ${\mathrm{B}}_2$-type structure for $x>\mathrm{}0.95\mathrm{}$. The ferromagnetic Curie temperature $T_C$ is enhanced from 115 K for Ce${\mathrm{Rh}}_3$ ${\mathrm{B}}_2$ to 125 K for Ce${\left({\mathrm{Rh}}_{0.8}{\mathrm{Ir}}_{0.2}\right)}_3$ ${\mathrm{B}}_2$, then decreases slowly to 118 K at $x=0.5\mathrm{}$ before decreasing sharply to 69 K at $x=0.67\mathrm{}$, even though the magnetic moment per Ce ion decreases monotonically with increasing Ir substitution. The $T_C$ of 125 K in Ce${\left({\mathrm{Rh}}_{0.8}{\mathrm{Ir}}_{0.2}\right)}_3$ ${\mathrm{B}}_2$ is the highest magnetic-ordering temperature observed so far for all Ce-based systems with nonmagnetic constituents.