Multipole ordering in f electron systems Original Research Article

We discuss multipole ordering in two cubic f-electron compounds. Field variation of the antiferroquadrupolar transition temperature TQ in PrPb3 is determined by the specific heat and the magnetization measurements. It is found that TQ(H) shows a pronounced increase for H∥〈100〉, which has been successfully explained by the antiferromagnetic interaction between the field-induced staggered moment in the O20(∝2Jz2−Jx2−Jy2) AFQ phase. From the analysis of the anisotropy in TQ(H), the importance of an octupolar interaction is pointed out. The new ordered state in CexLa1−xB6 (x<0.8), called phase IV, has been examined by magnetization measurements under uniaxial pressures. A pronounced anisotropy is observed at a relatively weak pressure, and the ordering temperature seems to increase in magnetic field. The results are discussed in view of a possible octupolar ordering in phase IV.