CeB6 Macroscopically Revisited

Magnetic susceptibility anisotropy and high sensitivity magnetostriction measurements are used to investigate the symmetry of CeB6 ordered states. The antiferromagnetic state is confirmed as tetragonal, but no deviation from the cubic symmetry is observed in the so-called antiferroquadrupolar phase, where only volume effects are detected. In this phase, the temperature dependence of the strain field susceptibilities is typical of nonordered quadrupoles. Moreover, while an antiferroquadrupolar order should be cubic, this symmetry is incompatible with the h < 1/2 1/2 1/2 > ordering wave vector. The antiferroquadrupolar description of CeB6 phase II is clearly inconsistent, and an alternative model, based on a unidimensional representation of the cube, has to be sought.