Pressure evolution of electronic and crystal structure of non-centrosymmetric EuCoGe3_3

We report on the pressure evolution of the electronic and crystal structures of the noncentrosymmetric antiferromagnet EuCoGe3. Using a diamond anvil cell, we performed high pressure fluorescence detected near-edge x-ray absorption spectroscopy at the Eu L3, Co K, and Ge K edges and synchrotron powder x-ray diffraction. In the Eu L3 spectrum, both divalent and trivalent Eu peaks are observed from the lowest pressure measurement (~2 GPa). By increasing pressure, the relative intensity of the trivalent Eu peak increases, and an average Eu valence continuously increases from 2.2 at 2 GPa to 2.31 at~50 GPa. On the other hand, no discernible changes are observed in the Co K and Ge K spectra as a function of pressure. With the increase in pressure, lattice parameters continuously decrease without changing I4mm symmetry. Our study revealed a robust divalent Eu state and an unchanged crystal symmetry of EuCoGe3 against pressure.Comment: Accepted in PRB https://journals.aps.org/prb/accepted/b2073O6fL9e1ca40307905b1de5bf05de12d8fc1

Low-Temperature Physical Properties of Single-Crystalline EuCoGe₃ and EuRhGe₃

Since a few years europium-based intermetallics have been attracting more and more attention due to their intriguing physical properties with anomalous behaviours in magnetically ordered states. Here, we report on the formation and the bulk physical properties of two tetragonal compounds EuCoGe₃ and EuRhGe₃, studied on high-quality single-crystalline specimens. In both materials, the Eu ions are in their divalent state, which gives rise to an antiferromagnetic ordering below $T_{N}$ = 15.4 K and $T_{N}$ = 11.3 K, respectively. In addition, EuCoGe₃ exhibits a successive antiferromagnetic phase transition at T₂ = 13.4 K. Based on some characteristic features in the temperature variations of the magnetic susceptibility, specific heat and electrical resistivity, we suggest that in both germanides an amplitude modulated magnetic structure develops below the respective $T_{N}$, with the Eu magnetic moments directed along the crystallographic [001] axis in EuCoGe₃ and perpendicular to this direction in EuRhGe₃