AC SUSCEPTIBILITY STUDIES OF THE UM(2)GE(2), TBM(2)GE(2), AND HOM(2)GE(2) COMPOUNDS (M=CO, NI, CU)

Polycrystalline samples of the compounds UM(2)Ge(2), TbM(2)Ge(2), and HoM(2)Ge(2) (M = Co, Ni, Cu) were studied by a.c. susceptibility measu rements from room temperature (RT) (295 K) to 80 K. The paramagnetic C urie temperature theta and effective magnetic moment mu(eff) were dete rmined. The variations in magnetic parameters with M in the U and Tb c ompounds are similar: T-N, RT chi(M), and mu(eff) decrease and theta i ncreases as M varies from Co to Cu. In the Ho compounds these paramete rs are quite constant, and the mu(eff) values are close to the free Ho 3+ ion value (4f(10) configuration). The higher mu(eff) values in UCo2 Ge2 (compared with 5f(1) to 5f(4)) and TbCo2Ge2 (compared with 4f(8)) are attributed to paramagnetic cobalt moments that do not order, and s uch moments decrease for nickel and disappear for copper.