Details

Autor(en) / Beteiligte

• de la Fuente, C.
• del Moral, A.
• Taylor, J.W.
• Adroja, D.T.

Titel

Vibron quasi-bound state stability for tetragonal CeCuxAg1-xAl3

Ist Teil von

• Journal of magnetism and magnetic materials, 2021-07, Vol.530, p.167541, Article 167541

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2021

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• •Study of the vibron quasi-bound state stability in CeCuxAg1-xAl3 (0.2 < x ≤ 1).•The vibron intensity depends on the phonon energy and oscillator strength.•There exists an effective attraction between pairs of 4f-electrons due to vibron. The vibron quasi-bound state stability was analyzed for the series of compounds CeCuxAg1-xAl3, 0.2 < x ≤ 1 (tetragonal phase) by using heat capacity and inelastic neutron scattering. The measurements of heat capacity show a significative reduction of ordering temperatures from 2.3 K at CeCu0.85Ag0.15Al3 down to 1.6 K for CeCu0.7Ag0.3Al3, increasing again up to 2.8 K for CeCu0.3Ag0.7Al3, while Kondo temperatures change from 9 K to 7 K. The electronic contribution of heat capacity, γ, slightly increases with unit-cell 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 two underlaying crystal-field excitations for cerium ions in paramagnetic regime well described according to Vegard’s law while the volume of the series CeCuxAg1-xAl3 compounds is increased. Additionally, a new magnetic excitation is found only in 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 suggests the presence of an effective attraction between pairs of 4f-electrons, which would explain the reduction of ordering temperatures for compounds with copper composition around 50%.