Magnetic order and multipole interactions inCexPr1−xB6solid solutions

Abstract

Magnetic ordering phenomena in ${\text{Ce}}_{x}{\text{Pr}}_{1\ensuremath{-}x}{\text{B}}_{6}$ 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 $(x\ensuremath{\le}0.7)$, Pr-Pr interactions play a dominant role, giving rise to incommensurate structures with wave vectors of the form ${\mathbf{k}}_{\text{IC}1}=(1/4\ensuremath{-}\ensuremath{\delta},1/4,1/2)$ or ${\mathbf{k}}_{\text{IC}2}=(1/4\ensuremath{-}\ensuremath{\delta},1/4\ensuremath{-}\ensuremath{\delta},1/2)$. 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.