Magnetic phase diagram in NdCu₄Ag single crystal

The magnetic properties of cubic intermetallic compound NdCu₄Ag single crystals were studied in detail through magnetization, susceptibility, specific heat and electrical resistivity measurements. An observed anomaly in C(T) with a sharp peak 26 J/(mol K) at 4.2 K, together with an antiferromagnetic behavior of X(T), indicated that an antiferromagnetic phase transition occurred at this temperature. Anisotropic properties in M(H), X(T), and C(T) at external fields were investigated in directions of [001], [110], and [111], respectively. Two metamagnetic transitions were observed below the Néel temperature T_N when a magnetic field was applied in three directions. In all the three directions, T_N decreased with an increase in magnetic field and new anomalies induced by a high H_ext were observed in both X(T) and C(T), implying that two new magnetic phases coexisted with the antiferromagnetic phase. From the specific heat measurements, it is speculated that the crystalline electric field ground state of Nd³⁺ (J = 9/2) ions is the G8 quartet for NdCu₄Ag. From these anomalies, the magnetic phase diagram of NdCu₄Ag was determined.