Screening effect on the multipole moments in the Kondo system CexLa1-xB6

We have performed specific heat, ultrasound, and magnetoresistivity measure ments examining the dense Kondo system Ce-0.5,La-0.5,B-6. The results obtai ned support the view that in the case of Ce0.5SLa0.5B6 a nonmagnetic state (the Kondo nonmagnetic state) exists due to the dense Kondo effect under lo w-temperature and low-held conditions. We have identified two characteristi c temperatures in Ce0.5La0.5B6. One is the Kondo temperature TK (5.5 simila r to 11 K), and the other is T-QC (similar to 1 K) which denotes the bindin g energy for the electric quadrupolar cancellation. In the CexLa1-xB6 syste m, T-K, is strongly dependent on the Ce concentration, whereas T-QC is almo st independent of it. The present results strongly suggest that phase IV ex ists in the range of 0.6 < x less than or equal to 0.75. The low-temperatur e specific heat of Ce0.65La0.35B6, in phase IV was found to be in proportio n to T-2 and this is difficult to interpret in terms of antiferromagnetic o rdering. The appearance of phase TV may arise from the pronounced discrepan cy between T-K and T-QC.