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We present a comprehensive study of the inhomogeneous mixed-valence compound, EuPd3S4, by electrical transport, X-ray diffraction, time-domain151Eu synchrotron Mössbauer spectroscopy, and X-ray absorption spectroscopy measurements under high pressure. Electrical transport measurements show that the antiferromagnetic ordering temperature,TN, increases rapidly from 2.8 K at ambient pressure to 23.5 K at ~19 GPa and plateaus between ~19 and ~29 GPa after which no anomaly associated withTNis detected. A pressure-induced first-order structural transition from cubic to tetragonal is observed, with a rather broad coexistence region (~20 GPa to ~30 GPa) that corresponds to theTNplateau. Mössbauer spectroscopy measurements show a clear valence transition from approximately 50:50 Eu2+:Eu3+to fully Eu3+at ~28 GPa, consistent with the vanishing of the magnetic order at the same pressure. X-ray absorption data show a transition to a fully trivalent state at a similar pressure. Our results show that pressure first greatly enhancesTN, most likely via enhanced hybridization between the Eu 4fstates and the conduction band, and then, second, causes a structural phase transition that coincides with the conversion of the europium to a fully trivalent state.
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Synthesis of Mixed‐Valent Lanthanide Sulfide Nanoparticles
Abstract In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed‐valent ferromagnets Eu3S4and EuSm2S4. Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu3S4, EuSm2S4, SmS1.9, and Sm3S4. All nanoparticle phases were identified using powder X‐ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence. The UV/Vis, Raman and X‐ray photoelectron spectroscopies for each phase were compared. Surprisingly, the phase is influenced by the halide and the reaction temperature, where EuCl2formed EuS while EuI2formed Eu3S4, highlighting the role of kinetics in phase stabilization. Interestingly, at lower temperatures EuI2initially forms EuS, and converts over time to Eu3S4.
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- Award ID(s):
- 1904616
- PAR ID:
- 10307938
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 60
- Issue:
- 43
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 23134-23141
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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