Synthesis, Physical, and Magnetocaloric Properties of MgZn₂-Type Gd₂Al₃Rh

Gd₂Al₃Rh was synthesized from the elements using arc-melting techniques, along with subsequent annealing. The title compound adopts the hexagonal MgZn₂ type structure (space group P6₃/mmc, hP12, Wyckoff sequence hfa) with the Gd atoms found on the Mg positions (4f), the Rh (2a) and Al (6h) atoms occupying the two Zn sites of the prototype. In addition, mixing of Rh and Al on both crystallographic positions is observed. The magnetic susceptibility and magnetization experiments were conducted indicating ferromagnetic ordering below the Curie temperature of T_C = 51.3(1) K and very high magnetization of 6.96(1) μ_B at 3 K and 70 kOe. In addition, heat capacity and electrical resistivity measurements were conducted. The magnetocaloric properties of ferromagnetic Gd₂Al₃Rh have been determined by means of magnetization measurements. For a field change of ΔH = 0 → 50 kOe the magnetic entropy change equals ΔS_M^max = -4.8 J kg^-1 K^-1, leading to a relative cooling power of RCP = 283 J kg^-1 for the same field change. The adiabatic temperature change was estimated to be ΔT_ad^max = 2.1 K using the heat capacity data.