Magnetic Properties of the 4 Sublattice Model for the Antiferro (AF) Quadrupolar Order Dominated by the AF Octupolar and AF Exchange Interactions –A Simple Model for CeB6–

The inconsistency between the results of NMR and neutron scattering in antiferro-quadrupolar (AFQ) ordered phase II of CeB 6 which remained to be solved over 15 years was explained recently by Sakai et al. by considering the O x y type AFQ ordering where the T x y z AF octupolar interaction plays an essential role. However, various unusual magnetic properties of the AF magnetic phase III and also phase II at low magnetic fields have remained to be explained. As a first step to understand these unusual properties of CeB 6 , we have carried out the mean field calculation for the 4 sublattice model where the sites are divided into two O x y quadrupolar sublattices dominated by the T x y z AF octupolar interaction and each of them is divided into two spin sublattices. Regardless of the simple 4 sublattice model, the calculated results could reproduce most of the unusual magnetic properties of CeB 6 . This strongly suggests that the O x y type AFQ ordering is realized in CeB 6 where both T x y z AF octupolar and AF exchange interactions play essential roles.