Ferromagnetic ordering and weak spin-glass-like effect in Pr(2)CuSi(3) and Nd(2)CuSi(3).

We present the results of the temperature dependences of ac and dc susceptibilities, high-field magnetization, magnetic relaxation, specific heat, and electrical resistivity of Pr(2)CuSi(3) and Nd(2)CuSi(3), compounds previously shown in the literature to exhibit interesting properties. It is observed that the investigated compounds undergo a ferromagnetic phase transition at a characteristic temperature T(C) (= 9.8 K for Pr(2)CuSi(3) and 5.6 K for Nd(2)CuSi(3)), where zero-field-cooled dc susceptibility shows a rapid increase followed by a sharp peak just below T(C). Below T(C), the magnetization curve displays an open hysteresis loop and a steep rise at low fields, while irreversible magnetism and long-time magnetic relaxation effects can be observed. Furthermore, near T(C) both the real and imaginary components of the ac susceptibility show a large peak with a small frequency shift of the peak position, and a sharp anomaly appears in the specific heat and electrical resistivity curves. These unusual features observed for Pr(2)CuSi(3) and Nd(2)CuSi(3) strongly suggest the formation of huge ferromagnetic clusters accompanied by a very weak spin-glass-like effect in both samples. The obtained results are discussed by comparing them with the data reported for other 2:1:3 intermetallic compounds and some alloyed compounds with different stoichiometry.