Abstract
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%.
Original language | English |
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Article number | 167541 |
Journal | Journal of Magnetism and Magnetic Materials |
Volume | 530 |
DOIs | |
Publication status | Published - 15 Jul 2021 |
Externally published | Yes |
Keywords
- 1.27.+a (Strongly correlated electron systems Heavy fermions)
- 71.70.Ch (Crystal and ligand fields)
- 75.30.Mb (Valence fluctuation, Kondo lattice, and heavy-fermion phenomena)
- 78.70.Nx (Neutron inelastic scattering)
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics