High Temperature Expansion for the Quadrupolar and the Octupolar Interactions

Abstract

The moment method for high temperature expansion (HTE) is applied to the coexistent system of interactions of (O_yz, O_zx, O_xy) quadrupole moments and of T_xyz octupole moment, both of which are indispensable for discussing the properties in phase I and II of CeB₆. The moments for HTE have been calculated up to fourth order exactly to give rise to the free energy and up to sixth order relevant to the susceptibility. The results are compared with those from the constant coupling approximation (CCA) to discuss the applicability of the CCA and HTE approximations. Comparison with the experimental results in phase I is also made to reveal the necessity of the interactions between the other moments to explain the properties of phase I, besides the dense Kondo effect being probably effective as well.