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| Main Authors: | , , |
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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2411.15052 |
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| _version_ | 1866916935124385792 |
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| author | Amara, Mehdi Opagiste, Christine Shitsevalova, Natalya Yu. |
| author_facet | Amara, Mehdi Opagiste, Christine Shitsevalova, Natalya Yu. |
| contents | In some intermetallic compounds, the crystallographic structure allows for an unusual latitude of movement of lanthanide ions inside so-called cages. Examples of such magnetic cage systems include the rare-earth hexaborides RB6 and filled skutterudites RPt4Ge12 series. In both instances, the rare-earth site, at the center of the cage, is of high symmetry, which may preserve some degree of orbital degeneracy. A deviation from the cage center lifts this degeneracy, yielding an interplay between the rare-earth movement and the system properties in the paramagnetic range. In particular, the low temperature thermal expansion should reflect this cage-specific crystal field contribution. This study presents an experimental investigation of the thermal expansion in the paramagnetic range of some elements in the aforementioned series. From a simple model for the vibrations in cage systems, a description of the phononic thermal expansion is proposed, within the quasi-harmonic approximation. Accounting for this non-magnetic contributions helps discern the influence of the orbital degeneracy at low temperature. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2411_15052 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Grüneisen rule in cubic rare-earth cage systems : the examples of LaB$_6$ and LaPt$_{4}$Ge$_{12}$ Amara, Mehdi Opagiste, Christine Shitsevalova, Natalya Yu. Strongly Correlated Electrons Materials Science In some intermetallic compounds, the crystallographic structure allows for an unusual latitude of movement of lanthanide ions inside so-called cages. Examples of such magnetic cage systems include the rare-earth hexaborides RB6 and filled skutterudites RPt4Ge12 series. In both instances, the rare-earth site, at the center of the cage, is of high symmetry, which may preserve some degree of orbital degeneracy. A deviation from the cage center lifts this degeneracy, yielding an interplay between the rare-earth movement and the system properties in the paramagnetic range. In particular, the low temperature thermal expansion should reflect this cage-specific crystal field contribution. This study presents an experimental investigation of the thermal expansion in the paramagnetic range of some elements in the aforementioned series. From a simple model for the vibrations in cage systems, a description of the phononic thermal expansion is proposed, within the quasi-harmonic approximation. Accounting for this non-magnetic contributions helps discern the influence of the orbital degeneracy at low temperature. |
| title | Grüneisen rule in cubic rare-earth cage systems : the examples of LaB$_6$ and LaPt$_{4}$Ge$_{12}$ |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2411.15052 |