0000000000303417
AUTHOR
Dirk Johrendt
Verwey-type transition in EuNiP
High temperature 151Eu 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 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.
Electronic structure studies ofBaFe2As2by angle-resolved photoemission spectroscopy
We report high resolution angle-resolved photoemission spectroscopy (ARPES) studies of the electronic structure of ${\text{BaFe}}_{2}{\text{As}}_{2}$, which is one of the parent compounds of the Fe-pnictide superconductors. ARPES measurements have been performed at 20 and 300 K, corresponding to the orthorhombic antiferromagnetic phase and the tetragonal paramagnetic phase, respectively. Photon energies between 30 and 175 eV and polarizations parallel and perpendicular to the scattering plane have been used. Measurements of the Fermi surface yield two hole pockets at the $\ensuremath{\Gamma}$ point and an electron pocket at each of the $X$ points. The topology of the pockets has been conclu…