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 determ ined by means of inelastic neutron scattering for x = 0.5, 1.0 and 1.75. Th e thermodynamic properties reconstructed from the obtained crystal-field pa rameters are compared to neutron diffraction, specific heat and magnetic su sceptibility 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 po int-charge model. It is concluded that Ga leads to an increase of the elect ron concentration and thus most likely triggers the structural phase transi tions in the RAlxGa2-x systems (R = rare earth) by a Hume-Rothery-like elec tronic mechanism. The experimentally observed large broadening of the cryst al-field transitions is discussed within the framework of concentration inh omogeneities.