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要旨:
High temperature Eu-151 Mossbauer 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 gamma-beta phase transition at T
approximate to 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
gamma-beta phase transition in compounds analogous to EuNiP.
