Low-temperature elastic constants of CeAl3

Abstract

Measurements of longitudinal and shear elastic constants in polycrystalline Ce${\mathrm{Al}}_3$ are presented. The measurements were extended to very low temperatures (50 mK). A strong softening for the longitudinal elastic constant was observed in the temperature region of the crystal-field splitting of ${\mathrm{Ce}}^{3+}$ (10-100 K), and an even stronger softening occurred below 4 K down to 0.6 K. Below 0.6 K down to 50 mK both elastic constants exhibit shallow minima. This behavior is correlated with other physical properties in the same temperature region. It is argued that one observes a transition from a region dominated by a single-ion Kondo effect of the crystal-field-split ${\mathrm{Ce}}^{3+}$ ion ($T>\mathrm{}0.6\mathrm{}$ K) to a new coherent state below 0.5 K.