LAUSR

Abstract The vibron quasi-bound state stability was analyzed for the series of compounds CeCuxAg1-xAl3, 0.2 γ , slightly increases with volume from 200 mJ/mol-K2 (x=0.85) to 210 mJ/mol-K2 (x=0.3), indicating small changes in the density of electronic states at Fermi level. The measurements of inelastic neutron scattering indicate the existence of underlaying two crystal field excitations for cerium ions in paramagnetic regime well described according with Vegard’s law while the volume of the series CeCuxAg1-xAl3 compounds is increased. Additionally, a new magnetic excitation is found only for CeCu0.85Ag0.15Al3 and CeCu0.7Ag0.3Al3 compounds that comes from the coupling between a crystal field excitation and a single “orthorhombic” phonon mode, via single ion magnetoelastic interaction. The intensity of this coupling increases from 0.4 meV/ion for CeCuAl3 to 0.7 meV/ion for CeCu0.7Ag0.3Al3, but after, it fades away for CeCu0.3Ag0.7Al3. The intensity of this coupling is highly dependent on the energy resonance between phonon mode and crystal field excitation, but also on the strength of the oscillator that vanishes when the volume of the unit cell increases sufficiently. Furthermore, the existence of this coupling also suggests the presence of an effective attraction between pairs of 4 f - electrons that would explain the reduction of ordering temperatures for compounds with copper composition around to 0.5.