Verwey-type transition in EuNiP

Abstract

High temperature 151 Eu Mössbauer measurements provide proof for inhomogeneous mixed-valent behaviour in EuNiP. We observed that EuNiP undergoes a Verwey-type charge delocalisation transition when heated above 470 K prior to the structural γ-β phase transition at T ≈ 510 K. This finding confirms the results of photoemission spectroscopy in the isostructural compound EuPdP and of TB-LMTO-ASA band structure calculations. We discuss the role of a van Hove singularity associated with a high density of 4f states close to the Fermi energy in inhomogeneous mixed europium valency, and the microscopic mechanism of γ-β phase transition in compounds analogous to EuNiP.

Fifty Years of Mössbauer Spectroscopy in Solid State Research – Remarkable Achievements, Future Perspectives

“…Mixed-valency and thermally induced transition between localized and delocalized valence states was observed with 151 Eu Mössbauer spectroscopy of the intermetallic compound EuNiP. [70] 151 Eu Mössbauer measurements between room temperature and ca. 500 K provide proof for mixed-valent behavior in the pnictide EuNiP ( Figure 32).…”

“…Variable temperature 151 Eu Mössbauer spectra of the intermetallic compound EuNiP. [70] becomes faster than the time-window of 151 Eu Mössbauer spectroscopy and above ca. 450 K the resonance signals of localized Eu 2+ (green) and Eu 3+ (blue) gradually disappear at the favor of a new signal with time-averaged oxidation state of Eu 2.5+ (red).…”

Structure and Properties of Mixed‐valence Compound Eu5Zr3S12

“…[14] crystallizes in a similar, but hexagonal structure with two crystallographic europium sites, namely one threefold and one twofold. This is suggestive of assigning the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 12 were selected directly from the samples and inspected by Laue photographs (white Mo-radiation). Single crystal intensity data were collected at room temperature on a STOE IPDS imaging plate detector (Mo-Kα, graphite-monochromator, ϕ-scan).…”

“…Inhomogeneous mixed-valence associated with Verwey-transitions have been observed in Eu 3 S 4 [7], Eu 4 As 3 [8] and in the metallic compounds EuPtP [9,10], EuPdAs [11] and EuNiP [12,13].…”

: Extent of charge ordering by Mössbauer spectroscopy and high-intensity high-resolution powder diffraction

“…The term Verwey transition has traditionally been used also for similar first-order transitions, such as in YFe 2 O 4 [18], LiMn 2 O 4 [19], Eu 3 O 4 [20] and EuNiP [21]. The recently synthesized [22] RBaFe 2 O 5 (R ¼ rare-earth atom) is the hitherto only such phase of the non-tilted perovskite type.…”