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 T-2 = 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.