Magnetic ordering phenomena in ${\text{Ce}}_x{\text{Pr}}_{1-x}{\text{B}}_6$ solid solutions have been studied using both powder and single-crystal neutron diffraction. A variety of magnetic structures are observed depending on temperature and Ce concentration. Over a broad composition range $\left(x\le 0.7\right)$, Pr-Pr interactions play a dominant role, giving rise to incommensurate structures with wave vectors of the form ${\mathbf{k}}_{\text{IC}1}=\left(1/4-\delta ,1/4,1/2\right)$ or ${\mathbf{k}}_{\text{IC}2}=\left(1/4-\delta ,1/4-\delta ,1/2\right)$. The crossover to a ${\text{CeB}}_6$-like regime takes place near $x=0.7–0.8$. For the latter composition, the antiferroquadrupolar phase transition observed in transport measurements precedes the onset, at lower temperature, of a commensurate magnetic order similar to that existing in ${\text{CeB}}_6$. However, unlike in the pure compound, an incommensurate magnetic order is formed at even higher temperature and persists in the antiferroquadrupolar phase down to the lock-in transition. These results are shown to reflect the interplay between various type of dipole exchange and higher multipole interactions in this series of compounds.

• Received 18 April 2008

DOI:https://doi.org/10.1103/PhysRevB.78.014415