Europhys. Lett.
Volume 74, Number 4, May 2006
Page(s) 672 - 678
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 05 April 2006
Europhys. Lett., 74 (4), pp. 672-678 (2006)
DOI: 10.1209/epl/i2005-10563-6

Verwey-type transition in $\chem{EuNiP}$

V. Ksenofontov1, Hem C. Kandpal1, J. Ensling1, M. Waldeck1, D. Johrendt2, A. Mewis2, P. Gütlich1 and C. Felser1

1  Institut für Anorganische Chemie und Analytische Chemie Johannes Gutenberg Universität - D-55099 Mainz, Germany
2  Institut für Anorganische Chemie und Strukturchemie II Heinrich-Heine-Universität - D-40225 Düsseldorf, Germany

received 8 December 2005; accepted in final form 10 March 2006
published online 5 April 2006

High temperature 151Eu Mössbauer measurements provide proof for inhomogeneous mixed-valent behaviour in $\chem{EuNiP}$. We observed that $\chem{EuNiP}$ undergoes a Verwey-type charge delocalisation transition when heated above $470\un{K}$ prior to the structural $\gamma$-$\beta$ phase transition at $T \approx 510\un{K}$. 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 $\chem{EuNiP}$.

71.20.-b - Electron density of states and band structure of crystalline solids.
76.80.+y - Mössbauer effect, other gamma-ray spectroscopy.

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