Crystal-field effects in Er₃RuAl₁₂with a distorted kagome lattice

We report on the magnetic and elastic properties of Er₃Ru₄Al₁₂ in static and pulsed magnetic fields up to 58 T. From the ultrasound results, we obtain evidence for a phase transition at 2 K related to magnetic ordering. Furthermore, in the paramagnetic state, Er₃Ru₄Al₁₂ shows pronounced anomalies in the magnetization and elastic moduli as a function of temperature and magnetic field. We explain our findings using a crystal-electricfield (CEF) model that includes quadrupolar interactions and propose a CEF level scheme for this material. However, the CEF effects cannot explain all field-induced anomalies, which indicates that refined models are needed for explaining these.