Ames Laboratory; Physics and Astronomy
Physics and Astronomy, Ames Laboratory
Physical Review B
Non-centrosymmetric Eu T Ge 3 ( T = Co, Ni, Rh, and Ir) possesses magnetic Eu 2 + ions, and antiferromagnetic ordering appears at low temperatures. Transition-metal substitution leads to changes in the unit-cell volume and in the magnetic ordering. However, the magnetic ordering temperature does not scale with the volume change, and the Eu valence is expected to remain divalent. Here we study the bulk electronic structure of non-centrosymmetric Eu T Ge 3 ( T = Co, Ni, Rh, and Ir) by hard x-ray photoelectron spectroscopy. The Eu 3 d core-level spectrum confirms the robust Eu 2 + valence state against the transition-metal substitution with a small contribution from Eu 3 + . The estimated Eu mean valence is around 2.1 in these compounds, as confirmed by multiplet calculations. In contrast, the Ge 2 p spectrum shifts to higher binding energy upon changing the transition metal from 3 d to 4 d to 5 d elements, hinting at a change in the Ge- T bonding strength. The valence bands of the different compounds are found to be well reproduced by ab initio band structure calculations.
Department of Energy Subject Categories
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
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