https://scholars.lib.ntu.edu.tw/handle/123456789/535720
標題: | The spin–orbit–phonon coupling and crystalline elasticity of LaCoO3 perovskite | 作者: | Guo-Jiun Shu Pei-Chieh Wub FANG-CHENG CHOU |
公開日期: | 十一月-2020 | 出版社: | The Royal Society of Chemistry | 卷: | 10 | 起(迄)頁: | 43117-43128 | 來源出版物: | RSC Advances | 摘要: | 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. |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/535720 | DOI: | 10.1039/D0RA09675J |
顯示於: | 凝態科學研究中心 |
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