Nonlinear susceptibility measurement for quadrupolar response in a dilute Γ₃ Non-Kramers Doublet System Pr_0.05La _0.95Pb₃

We measure the temperature dependence of the nonlinear susceptibility Χ3, which reflects the fluctuation of quadrupolar moments, in Pr _0.05La_0:95Pb₃ with a Γ3 non-Kramers doublet in the crystal-electric-field ground state to provide evidence of the quadrupolar Kondo effect. Non-Fermi liquid behavior of Χ3 with a -ln T dependence is detected in the [100] and [110] directions below T ≈ 2:5 K, suggesting the screening of quadrupolar moments. In contrast, Χ3 in the [111] direction becomes constant below T ≈ 3 K. The observed features indicate that a low-lying Γ₃ doublet plays a crucial role in the anomalous properties of Pr_xLa_1-xPb₃.