Magnetic and acoustic anomalies of UCu_0.95Ge in high magnetic fields

Magnetic and magneto-acoustic properties of the intermetallic compound UCu_0.95Ge with antiferromagnetic ground state have been investigated on single crystals in pulsed magnetic fields up to 64 T. A first-order phase transition has been observed for fields applied along the a and c axis at 61 and 38 T, respectively. In both directions, the magnetization trends to saturate at 1.35 _μB per formula unit. These field-induced transitions as well as the antiferromagnetic ordering at T_N = 48 K are accompanied by pronounced anomalies in the sound velocity and sound attenuation. Additionally, the acoustic characteristics show some unusual frequency-dependent features which presumably can be related to the dynamics of Cu vacancies [1]. The field-temperature phase diagrams are constructed for both magnetic-field directions. The experimental data are analyzed by use of the mean-field approximation and agree qualitatively with the obtained results.