Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

We investigated the elastic properties of Y_1−xNd_xCo₂Zn₂₀ with localized Nd f electrons and ground-state Kramers doublet. All longitudinal and transverse moduli of NdCo₂Zn₂₀ (x = 1) show an elastic softening below 50 K accompanied by a minimum around 2.5 K. The softening, which is robust to magnetic fields up to 8 T, is not observed for samples with Nd concentrations of x = 0.19, 0.05, and 0. In localized f electron systems, elastic softening from high temperatures is often understood by crystal electric field effects; however, this cannot explain the behavior in NdCo₂Zn₂₀. Our experimental and calculated results reveal that the softening neither is caused by a phonon contribution, a Nd³⁺ single-site effect, nor a magnetic interaction. We conclude that the softening is due to a local-symmetry-sensitive electronic state in NdCo₂Zn₂₀.