The spin–orbit–phonon coupling and crystalline elasticity of LaCoO3 perovskite
| Autor: | Guo-Jiun Shu, Pei-Chieh Wu, F. C. Chou |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Materials science
Condensed matter physics Band gap Phonon General Chemical Engineering Electron energy loss spectroscopy 02 engineering and technology General Chemistry Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences Magnetic susceptibility Thermal expansion Bond length 0103 physical sciences Condensed Matter::Strongly Correlated Electrons 010306 general physics 0210 nano-technology Excitation |
| Zdroj: | RSC Advances. 10:43117-43128 |
| ISSN: | 2046-2069 |
| DOI: | 10.1039/d0ra09675j |
| Popis: | Based on an integrated study of magnetic susceptibility, specific heat, and thermal expansion of single-crystal LaCoO3 free from cobalt and oxygen vacancies, two narrow spin gaps are identified before and after the phonon softening of gap size ΔE ∼ 0.5 meV in a CoO6-octahedral crystal electric field (CEF) and the thermally activated spin gap Q ∼ 25 meV, respectively. Significant excitation of Co3+ spins from a low-spin (LS) to a high-spin (HS) state is confirmed by the thermal activation behavior of spin susceptibility χS of energy gap Q ∼ 25 meV, which follows a two-level Boltzmann distribution to saturate at a level of 50% LS/50% HS statistically above ∼200 K, without the inclusion of a postulated intermediate spin (IS) state. A threefold increase in the thermal expansion; coefficient (α) across the same temperature range as that of thermally activated HS population growth is identified, which implies the non-trivial spin–orbit–phonon coupling caused the bond length of Co3+(LS↔HS)–O fluctuation and the local lattice distortion. The unusually narrow gap of ΔE ∼ 0.5 meV for the CoO6 octahedral CEF between eg–t2g indicates a more isotropic negative charge distribution within the octahedral CEF environment, which is verified by the Electron Energy Loss Spectroscopy (EELS) study to show nontrivial La–O covalency. |
| Databáze: | OpenAIRE |
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