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Pressure evolution of the electronic structure of non-centrosymmetric EuRhGe3

Among europium compounds, pressure induced valence transition and/or intermediate valence state is often observed. In such systems, applying several GPa of pressure can drive a Eu valence from divalent to almost trivalent. Non-centrosymmetric EuRhGe3 possesses magnetic Eu2+ ions and exhibits antiferromagnetic ordering ∼11 K at ambient pressure. Pressure resistant magnetic ordering and stable divalent Eu state have been reported in EuRhGe3 . Here we study the pressure evolution of Eu valence of EuRhGe3 by x-ray absorption spectroscopy using partial fluoresence yield method. Our study revealed a successive increase of Eu valence by applying pressure without a first order valence transition. The obtained Eu mean valence approaches ∼2.4 around 40 GPa at 300 K but not fully become trivalent. Pressure evolution of the electronic structure is also studied by density functional theoretical approach. Our theoretical analysis suggests that the increase of Eu valence obtained by Eu L3 spectra is caused by an increase of Eu 5d orbital occupation but that of Eu 4f stays almost 4f 7 . Possibly the magnetic moments of Eu 4f 7 persist through the measurement pressure range, at least up to ∼ 40 GPa.

eu valence ; pressure ; x-ray absorption ; electronic structure

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