Magnetocaloric effect, magnetothermal and elastic properties of SmFe₃ and ErFe₃ compounds

We report on the temperature and field dependences of magnetization, magnetic specific heat, and magnetic entropy of the ferromagnetic SmFe₃ (T_C & 655 K) and ferrimagnetic ErFe₃ (T_C ≈ 600 K, compensation temperature & 230 K) compounds using the mean-field theory (MFT). The magnetocaloric effect (MCE), namely, the isothermal change in entropy (ΔS_m) and the adiabatic change in temperature (DT ad ), is determined using the well-known Maxwell relation. Density Functional Theory (DFT), as implemented in the WIEN2k electronic code, is used to perform the ab- initio calculation of the elastic constants, bulk and shear moduli, and density-of-states. Using the electronic coefficient of specific heat (γ_e) and the Debye temperature (θ_D), the electronic and lattice contributions to the total specific heat and total entropy are computed, respectively. The ferrimagnetic ErFe₃ exhibits both direct and inverse MCE, while SmFe₃ exhibits only direct MCE effects. For SmFe₃ , the maximum ΔS_m for a 7T field change is approximately 1.29 J/mol K. For the same field change, the maximum direct and inverse ΔS_m for ErFe₃ are approximately 0.69 and 0.74 J/mol K, respectively. At their respective Curie temperatures, SmFe₃ and ErFe₃ exhibit adiabatic temperature changes of about 8 and 5 K, respectively, for a 7 T field change. The Arrott plots and universal curves, along with specific aspects of the thermo-magnetic and magnetocaloric properties, are used to examine the order of the magnetic phase transition in these two systems. (author)