Elemental Dilution Effect on the Elastic Response due to a Quadrupolar Kondo Effect of the Non-Kramers System Y₁₋<i>_x</i>Pr<i>_x</i>Ir₂Zn₂₀

We measured the elastic constants (C11 − C12)/2 and C44 of non-Kramers system Y0.63Pr0.37Ir2Zn20 (Pr-37% system) by means ultrasound to check how single-site quadrupolar Kondo effect is modified increasing Pr concentration. The Curie-like softening present Pr-37% on cooling from 5 1 K can be reproduced a multipolar susceptibility calculation based Γ3 doublet crystalline-electric-field ground state. Further, below 0.15 K, temperature dependence proportional \(\sqrt{T} \) was observed in C12)/2. This behavior rather corresponds theoretical prediction “lattice” model, unlike that Pr-3.4% system, which shows logarithmic “single-site” theory. In addition, we discuss possibility form vibronic state coupling between low-energy phonons electric quadrupoles since found ultrasonic dispersion range K.