Magnetic properties and hyperfine interactions in EuCu sub(2)Ge sub(2) single crystals

The results of X-ray diffraction, magnetic susceptibility, and super(151)Eu Moessbauer spectroscopy studies of single crystals of EuCu sub(2)Ge sub(2) grown by a flux method are reported. The magnetic susceptibility and Moessbauer data clearly demonstrate the divalent state of Eu in the temperature range 2-300 K. These data also show that EuCu sub(2)Ge sub(2) 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) degree away from the c-axis. The Debye temperature of EuCu sub(2)Ge sub(2) determined from the Moessbauer data is 226(2) K. The origin of the differences in magnetic properties of single-crystal and polycrystalline samples of EuCu sub(2)Ge sub(2) is discussed in terms of chemical pressure.