Magnetic ordering in ternary germanide Nd₂CuGe₆

We have performed a systematic investigation on a well-annealed polycrystalline Nd₂CuGe₆ sample by measuring its AC and DC susceptibility χ(T), magnetization M(H), magnetic relaxation M(t), electrical resistivity ρ(T) and specific heat C(T). The sharp peak observed at about T_N = 9.4 K in χ_AC(T), χ_DC(T) and C(T) curves, respectively, indicates the occurrence of an antiferromagnetic order, which is further confirmed by the sudden decrease in ρ(T) at the same temperature. In the magnetically ordered state, M(H) shows an evident metamagnetic transition. Moreover, the χ_DC(T) and M(t) measurements reveal evident irreversible magnetism and long-time magnetic relaxation effect below T_N indicating the metastable characters of the magnetically ordered state. The formation of the metastable magnetic state cannot be explained as glass freezing of the neodymium magnetic moments in the Ce₂CuGe₆-type orthorhombic Nd₂CuGe₆ sample.