Magnetic study of low-temperature phase of UCu2Ge2

Magnetization and phase sensitive AC susceptibility was measured for the annealed and as-cast samples of ferromagnetic UCu2Ge2, TC=107K. Special attention was paid to the low temperature range, T<50K, which is interesting due to the magnetization decrease and frozen AC response. The hysteresis loops showed a remanence of ≈87% and a fast, thermally activated decrease in the coercivity field. Thermoremanent magnetization at 4.3 K decayed with the relaxation time ≈1∗103 s. The strong increase of the χACχAC with the amplitude of the driving field was observed. All these results point to a very large anisotropy of the compound at the lowest temperatures. Phase transition to the randomly canted ferromagnetic phase at T≈55K was detected in the measurement of the third order non-linear susceptibility. It is concluded that the origin of the transition is the strong temperature dependence of magnetic anisotropy.