Magnetic properties and hyperfine interactions in EuCu_2Ge _2 single crystals

摘要

The results of X-ray diffraction, magnetic susceptibility, and ~(151)Eu Mssbauer spectroscopy studies of single crystals of EuCu _2Ge_2 grown by a flux method are reported. The magnetic susceptibility and Mssbauer data clearly demonstrate the divalent state of Eu in the temperature range 2300 K. These data also show that EuCu_2Ge _2 is an antiferromagnet with two antiferromagnetic transitions at 5.3(1) and 8.2(1) K in contrast to one antiferromagnetic transition at 1314 K observed for polycrystalline samples. The direction of the Eu magnetic moment at 2.0 K is 49(2)° away from the c-axis. The Debye temperature of EuCu _2Ge_2 determined from the Mssbauer data is 226(2) K. The origin of the differences in magnetic properties of single-crystal and polycrystalline samples of EuCu_2Ge_2 is discussed in terms of chemical pressure.