Magnetic phase transitions and magnetocaloric effect in ternary rhombohedral Laves phases of Gd₂Rh₃Ge and Er₂Rh₃Ge

Magnetic phase transitions in two Mg₂Ni₃Si-type of Gd₂Rh₃Ge and Er₂Rh₃Ge compounds (space group R3‾m, hR18) belonging to rhombohedral Laves phases are studied in this paper. Structural investigations using X-ray diffraction and subsequent Rietveld analysis confirm the rhombohedral R3‾m Laves phase for both compounds. Magnetization as a function of temperature, M(T), identifies the ferromagnetic transition temperature in both samples with T_C = 64 K and 20 K for Gd₂Rh₃Ge and Er₂Rh₃Ge respectively which is supported by the specific heat, C_p(T). Arrott plots, universal scaling curves by normalizing magnetic entropy changes (ΔS_m) and field dependent ΔS_m revealed that both compounds undergo second order ferromagnetic phase transitions at T_C. Significant magnetocaloric effect (MCE) is observed for both compounds, attaining a value of 12 J kg⁻¹ K⁻¹ at T = 64 K, H = 7 T for Gd₂Rh₃Ge and 11 J kg⁻¹ K⁻¹ at T = 20 K, H = 7 T for Er₂Rh₃Ge. The adiabatic temperature change is 5.9 K for Gd₂Rh₃Ge and 10.5 K for Er₂Rh₃Ge for H = 7 T.