Magnetic and thermal properties of cubic single-crystal PrCu₄Ag

We succeeded in synthesizing a new cubic intermetallic compound PrCu ₄Ag in a fcc structure. Measurements of X-ray diffraction, magnetic susceptibility, magnetization, specific heat, electrical resistivity, thermal expansion, and elastic constants have been performed on single crystals of PrCu₄Ag. A maximum value of χ(T) with a corresponding peak in C(T) suggests that an antiferromagnetic phase transition occurs at T_N = 2.4 K, where a sudden decrease in ρ_4f (T) and a sharp peak in the thermal expansion coefficient α(T) were observed. Characteristic Curie-type softening was observed in the temperature dependence of the transverse mode for (C₁₁ - C₁₂)=2 and C44 from 70K down to TN, which implies that the crystalline electric field (CEF) ground state is the magnetic triplet τ5. The anisotropic properties in M(T,H) and C(T,H) are studied when the external magnetic field is applied in the (100), (110), and (111) directions. Another anomaly observed at approximately 10K in χ(T) is considered to be related to possible disorder behavior. The low-T behavior and the possibility of quadrupole fluctuation are discussed with respect to the CEF effect. All the experimental results in the present study are summarized in a magnetic phase diagram.