Quadrupolar phase transition and field-dependent multipolar fluctuation inCeB6

The effect of multipolar fluctuations on the quadrupolar phase transition i n CeB6 is investigated. The d(-1)-correction to Hie mean-field solution of the multipolar Ruderman-Kittel-Kasuya-Yoshida (RKKY) model is analyzed in t erms of a generalized Landau expansion of free energy, with d being the spa tial dimension. It Ls shown that the multipolar fluctuations become strong and field-dependent when the model is close to the SU(4)-symmetric limit. A s a result, various unusual phenomena around the transition are shown to be reasonably explained within the RKKY model. The realistic form of the inte ractions for CeB6 is discussed oil the basis of a quantitative comparison w ith experiments.