Ferromagnetic ordering and weak spin-glass-like effect in Pr ₂CuSi₃ and Nd₂CuSi₃

We present the results of the temperature dependences of ac and dc susceptibilities, high-field magnetization, magnetic relaxation, specific heat, and electrical resistivity of Pr₂CuSi₃ and Nd ₂CuSi₃, compounds previously shown in the literature to exhibit interesting properties. Itis observed that the investigated compounds undergo a ferromagnetic phase transition at a characteristic temperature T _C (=9.8K for Pr₂CuSi₃ and 5.6K for Nd ₂CuSi₃), 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 Pr₂CuSi₃ and Nd₂CuSi₃ 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.