A study of elastic properties of URu₂Si₂ in comparison with the non-5f contribution of ThRu₂Si₂

Ultrasonic investigations of the elastic constants of non-5f compound ThRu2Si2 were performed in order to highlight possible quadrupolar response in the elastic constants of heavy fermion compound URu2Si2, by using the ThRu2Si2 for backgrounds to subtract the phonon contributions in the elastic constants of URu2Si2. We confirmed that the all-elastic constants of ThRu2Si2 show no elastic anomaly, i.e., increasing monotonically and saturating toward low temperatures, which can be understood regular phonon contributions for the solid states. The background-subtracted (C11-C12)/2 of URu2Si2 keeps decreasing with decreasing temperatures from 300 K, while other share modes C44 and C66 show little change. These contrasts suggest that the Γ3-type quadrupole moment O2² will be still dominant and active in URu2Si2 at low temperatures.