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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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Fluorides of Silver Under Large Compression**
Abstract The silver‐fluorine phase diagram has been scrutinized as a function of external pressure using theoretical methods. Our results indicate that two novel stoichiometries containing Ag+and Ag2+cations (Ag3F4and Ag2F3) are thermodynamically stable at ambient and low pressure. Both are computed to be magnetic semiconductors under ambient pressure conditions. For Ag2F5, containing both Ag2+and Ag3+, we find that strong 1D antiferromagnetic coupling is retained throughout the pressure‐induced phase transition sequence up to 65 GPa. Our calculations show that throughout the entire pressure range of their stability the mixed‐valence fluorides preserve a finite band gap at the Fermi level. We also confirm the possibility of synthesizing AgF4as a paramagnetic compound at high pressure. Our results indicate that this compound is metallic in its thermodynamic stability region. Finally, we present general considerations on the thermodynamic stability of mixed‐valence compounds of silver at high pressure.
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- Award ID(s):
- 1827815
- PAR ID:
- 10220730
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 27
- Issue:
- 17
- ISSN:
- 0947-6539
- Format(s):
- Medium: X Size: p. 5536-5545
- Size(s):
- p. 5536-5545
- Sponsoring Org:
- National Science Foundation
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