Temperature-induced valence transition in EuNi2(Si1–Ge )2 investigated by high-energy resolution fluorescence detection X-ray absorption spectroscopy

Shimokasa, Ryohei; Kawamura, N.; Matsumoto, Takayuki; Kawakami, Koki; Taku, Kawabata; Isumi, Gen; Uozumi, Takayuki; Mitsuda, Akihiro; Wada, Hirofumi; Mizumaki, Masaichiro; Mimura, Koji

doi:10.1016/j.radphyschem.2019.02.009

Cited by 7 publications

(2 citation statements)

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“…In contrast, S 2 , S 3 , and S 4 , accompanying peak B, appear at temperatures below T v . Our previous report on the HERFD-XAS experiments for EuNi 2 (Si 1-x Ge x ) 2 has also mentioned the existence of additional fine structures in the spectra [18]. The S 4 spectral intensity of Eu(Rh 1-…”

Section: Resultsmentioning

confidence: 89%

Electronic Structure of the Valence Transition System Eu(Rh₁₋_xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Shimokasa

Kawamura

Taku

et al. 2020

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)

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The electronic structure of Eu(Rh 1-x T x) 2 Si 2 (T = Co, Ir) showing a valence change with temperature has been investigated by means of high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS). The Eu L 3-edge HERFD-XAS spectra for Eu(Rh 1-x T x) 2 Si 2 distinctly demonstrate that, due to the improvement of the energy resolution, the intensities of Eu 2+ and Eu 3+ components are dependent on temperature. Each component has additional fine structures, which clearly change above and below the transition temperature. These spectral changes are similar to those for EuNi 2 (Si 1-x Ge x) 2 , but the degree of temperature dependence on energy difference between Eu 2+ and Eu 3+ components is different from EuNi 2 (Si 1-x Ge x) 2. The results of this study suggest that a treatment of the many-body interaction is essential to understanding the valence transition of Eu compounds.

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Section: Resultsmentioning

confidence: 89%

Electronic Structure of the Valence Transition System Eu(Rh₁₋_xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Shimokasa

Kawamura

Taku

et al. 2020

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)

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“…Recently, there have been remarkable advances in using in situ and operand techniques, which enable real-time observation of surface reactions on catalysts and battery electrodes. It is now possible to obtain high-resolution XAFS spectra free from the core-hole lifetime broadening by detecting monochromatized fluorescence [84].…”

Section: G Development Of Surface and Interface Science Using Hard X-...mentioning

confidence: 99%

Progress of Surface and Interface Science Using Synchrotron Radiation

Kinoshita

2023

e-J. Surf. Sci. Nanotechnol.

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4f electron temperature driven ultrafast electron localization

Yamagami,

Ueda,

Staub

et al. 2024

Phys. Rev. Research

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Valence transitions in strongly correlated electron systems are caused by orbital hybridization and Coulomb interactions between localized and delocalized electrons. The transition can be triggered by changes in the electronic structure and is sensitive to temperature variations, applications of magnetic fields, and physical or chemical pressure. Launching the transition by photoelectric fields can directly excite the electronic states and thus provides an ideal platform to study the correlation among electrons on ultrafast timescales. The EuNi2(Si0.21Ge0.79)2 mixed-valence metal is an ideal material to investigate the valence transition of the Eu ions via the amplified orbital hybridization by the photoelectric field on subpicosecond timescales. A direct view on the 4f electron occupancy of the Eu ions is required to understand the microscopic origin of the transition. Here we probe the 4f electron states of EuNi2(Si0.21Ge0.79)2 at the sub-ps timescale after photoexcitation by x-ray absorption spectroscopy across the Eu M5-absorption edge. The observed spectral changes due to the excitation indicate a population change of total angular momentum multiplet states J = 0, 1, 2, and 3 of Eu3+ and the Eu2+ J = 7/2 multiplet state caused by an increase in 4f electron temperature that results in a 4f localization process. This electronic temperature increases combined with fluence-dependent screening accounts for the strongly nonlinear effective valence change. The data allow us to extract a time-dependent determination of an effective temperature of the 4f shell, which is also of great relevance in the understanding of metallic systems' properties, such as the ultrafast demagnetization of ferromagnetic rare-earth intermetallic and their all-optical magnetization switching. In addition, our results elucidate the energetics of charge fluctuations in valence-mixed electronic systems, which provide enriched knowledge regarding the role of valence transitions and orbital hybridization for quantum critical phenomena. Published by the American Physical Society 2024

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Temperature-induced valence transition in EuNi2(Si1–Ge )2 investigated by high-energy resolution fluorescence detection X-ray absorption spectroscopy

Cited by 7 publications

References 25 publications

Electronic Structure of the Valence Transition System Eu(Rh₁₋_xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Electronic Structure of the Valence Transition System Eu(Rh₁₋_xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Progress of Surface and Interface Science Using Synchrotron Radiation

4f electron temperature driven ultrafast electron localization

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Temperature-induced valence transition in EuNi2(Si1–Ge )2 investigated by high-energy resolution fluorescence detection X-ray absorption spectroscopy

Cited by 7 publications

References 25 publications

Electronic Structure of the Valence Transition System Eu(Rh1−xTx)2Si2 (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Electronic Structure of the Valence Transition System Eu(Rh1−xTx)2Si2 (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Progress of Surface and Interface Science Using Synchrotron Radiation

4f electron temperature driven ultrafast electron localization

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Electronic Structure of the Valence Transition System Eu(Rh₁₋_xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Electronic Structure of the Valence Transition System Eu(Rh₁₋_xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy