Crystal-field interactions in the pseudo-ternary compound ErAlxGa2-x studied by inelastic neutron scattering

The crystal field of the pseudo-ternary compound ErAlxGa2-x has been determined by means of inelastic neutron scattering for x=0.5, 1.0 and 1.75. The thermodynamic properties reconstructed from the obtained crystal-field parameters are compared to neutron diffraction, specific heat and magnetic susceptibility measurements. The effect of increasing the Ga concentration on the crystal-field potential with respect to the change in geometry and the electronic properties of the solid is discussed by means of an extended point-charge model. It is concluded that Ga leads to an increase of the electron concentration and thus most likely triggers the structural phase transitions in the RAlxGa2-x systems (R=rare earth) by a Hume-Rothery-like electronic mechanism. The experimentally observed large broadening of the crystal-field transitions is discussed within the framework of concentration inhomogeneities. (author)