Pressure-Induced Valence Transition and Heavy Fermion State in Eu2Ni3Ge5 and EuRhSi3

Nakamura, Ai; Okazaki, Tomoya; Nakashima, Miho; Amako, Yasushi; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Kayama, Shuei; Kagayama, Tomoko; Shimizu, Katsuya; Uejo, Taro; Akamine, Hikaru; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika; Shibata, Hiroyuki

doi:10.7566/jpsj.84.053701

Cited by 25 publications

(12 citation statements)

References 15 publications

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“…We do not however find a logarytmic dependence of ρ as T → 0, which is a characteristic feature of Kondo scattering with magnetic impurities 51,52 . The growth of ρ(T ) below T N observed in Nd 1−x La x NiC 2 does not lead to a maximum as reported in antiferromagnets with dominance of Kondo interactions 53,54 . In these systems, resistivity drops significantly below the magnetic ordering temperature due to the suppression of spin disorder scattering as in regular AFM metals.…”

Section: Resultssupporting

confidence: 52%

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

et al. 2019

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The path from the charge density wave antiferromagnet NdNiC2 to a noncentrosymmetric superconductor LaNiC2 has been studied by gradual replacement of Nd by La ions. The evolution of physical properties has been explored by structural, magnetic, transport, magnetoresistance and specific heat measurements. With the substitution of La for Nd, the Peierls temperature is gradually suppressed, which falls within the BCS mean-field relation for chemical pressure with a critical concentration of xc = 0.38. As long as charge density wave is maintained, the antiferromagnetic ground state remains robust against doping and despite of a Nel temperature reduction shows a rapid and sharp magnetic transition. Once the CDW is completely suppressed, intermediate compounds of the Nd1−xLaxNiC2 series reveal symptoms of a gradual softening of the features associated with AFM transition and increase of the spin disorder. Immediately after the antiferromagnetic transition is depressed to zero temperature, the further incorporation of La ions results in the emergence of superconductivity. This crossover in the Nd1−xLaxNiC2 is discussed in the terms of the possible quantum critical point.

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Section: Resultssupporting

confidence: 52%

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

et al. 2019

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“…The conversion from divalent EuRh 2 Si 2 to valence-fluctuating EuIr 2 Si 2 involves only a ∼1.5% volume change, indicating its origins in electronic structure changes 15 . Very recently, exotic behavior has been discovered in EuRhSi 3 and Eu 2 Ni 3 Ge 5 [16][17][18] that cannot be explained by the conventional phase diagram of Eucompounds. Both EuRhSi 3 and Eu 2 Ni 3 Ge 5 have magnetic Eu 2+ ions and exhibit antiferromagnetism below T N =49 K and 19 K, respectively, at ambient pressure.…”

Section: Introductionmentioning

confidence: 99%

Bulk electronic structure of non-centrosymmetric EuTGe3 ( T=Co , Ni, Rh, Ir) studied by hard x-ray photoelectron spectroscopy

et al. 2018

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Non-centrosymmetric EuT Ge3 (T =Co, Ni, Rh, and Ir) possesses magnetic Eu 2+ ions and antiferromagnetic ordering appears at low temperatures. Transition metal substitution leads to changes of the unit cell volume and of the magnetic ordering. However, the magnetic ordering temperature does not scale with the volume change and the Eu valence is expected to remain divalent. Here we study the bulk electronic structure of non-centrosymmetric EuT Ge3 (T =Co, Ni, Rh, and Ir) by hard x-ray photoelectron spectroscopy. The Eu 3d core level spectrum confirms the robust Eu 2+ valence state against the transition metal substitution with a small contribution from Eu 3+ . The estimated Eu mean-valence is around 2.1 in these compounds as confirmed by multiplet calculations. In contrast, the Ge 2p spectrum shifts to higher binding energy upon changing the transition metal from 3d to 4d to 5d elements, hinting of a change in the Ge-T bonding strength. The valence bands of the different compounds are found to be well reproduced by ab initio band structure calculations.

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“…However, recently, the heavy-electron state in Eu compounds, just at the center in lanthanide series, have attracted renewed attention. [38][39][40][41][42] In the divalent ion of europium, seven electrons are accommodated in the 4f orbitals, while in the trivalent ion of europium, we find six 4f electrons. In an LS coupling scheme, due to the Hund's rules, we obtain J = S = 7/2 and L = 0 for Eu 2+ , where J, S, and L indicate, respectively, total angular momentum, total spin momentum, and total orbital momentum.…”

Section: Introductionmentioning

confidence: 76%

“…Thus, the valence fluctuation is one of key issues in Eu compounds. 40) Quite recently, in Eu 2 Ni 3 Ge 5 and EuRhSi 3 , heavy-electron states have been claimed to be observed in the temperature 42) (b) LS coupling scheme (a) j-j coupling scheme j=5/2 j=7/2 Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

Effect of Spin–Orbit Coupling on Kondo Phenomena in f⁷-Electron Systems

Hotta

2015

J. Phys. Soc. Jpn.

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In order to promote our basic understanding on the Kondo behavior recently observed in europium compounds, we analyze an impurity Anderson model with seven f electrons at an impurity site by employing a numerical renormalization group method. The local part of the model consists of Coulomb interactions among f electrons, spin-orbit coupling λ, and crystalline electric field (CEF) potentials, while we consider the hybridization V between local f electrons and single-band conduction electrons with au symmetry. For λ = 0, we observe the underscreening Kondo behavior for appropriate values of V , characterized by the entropy change from ln 8 to ln 7, in which one of seven f electrons is screened by conduction electrons. When λ is increased, we obtain two types of behavior depending on the values of V . For large V , we find the entropy release of ln 7 at low temperatures, determined by the level splitting energy due to the hybridization. For small V , we also observe the entropy change from ln 8 to ln 2 by the level splitting due to the hybridization, but at low temperatures, ln 2 entropy is found to be released, leading to the Kondo effect. We emphasize that the Kondo behavior for small V is observed for realistic values of λ in the order of 0.1 eV. We also discuss the effect of CEF potentials and the multipole properties in the Kondo behavior found in this paper.

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Pressure-Induced Valence Transition and Heavy Fermion State in Eu₂Ni₃Ge₅ and EuRhSi₃

Cited by 25 publications

References 15 publications

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

Bulk electronic structure of non-centrosymmetric EuTGe3 ( T=Co , Ni, Rh, Ir) studied by hard x-ray photoelectron spectroscopy

Effect of Spin–Orbit Coupling on Kondo Phenomena in f⁷-Electron Systems

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Pressure-Induced Valence Transition and Heavy Fermion State in Eu2Ni3Ge5 and EuRhSi3

Cited by 25 publications

References 15 publications

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd1−xLaxNiC2 compounds

Bulk electronic structure of non-centrosymmetric EuTGe3 ( T=Co , Ni, Rh, Ir) studied by hard x-ray photoelectron spectroscopy

Effect of Spin–Orbit Coupling on Kondo Phenomena in f7-Electron Systems

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Pressure-Induced Valence Transition and Heavy Fermion State in Eu₂Ni₃Ge₅ and EuRhSi₃

Effect of Spin–Orbit Coupling on Kondo Phenomena in f⁷-Electron Systems