Magnetic properties and hyperfine interactions in EuCu2Ge2 single crystals

The results of X-ray diffraction, magnetic susceptibility, and 151Eu Mössbauer spectroscopy studies of single crystals of EuCu2Ge2 grown by a flux method are reported. The magnetic susceptibility and Mössbauer data clearly demonstrate the divalent state of Eu in the temperature range 2–300 K. These data also show that EuCu2Ge2 is an antiferromagnet with two antiferromagnetic transitions at 5.3(1) and 8.2(1) K in contrast to one antiferromagnetic transition at 13–14 K observed for polycrystalline samples. The direction of the Eu magnetic moment at 2.0 K is 49(2)° away from the cc-axis. The Debye temperature of EuCu2Ge2 determined from the Mössbauer data is 226(2) K. The origin of the differences in magnetic properties of single-crystal and polycrystalline samples of EuCu2Ge2 is discussed in terms of chemical pressure.