Magnetothermal Properties and Magnetocaloric Effect in some RFe_2 Compounds.

Abstract

Temperature dependence of magnetization shows that ErFe_2 is ferrimagnetic with compensation point around 471 K and Curie temperature close to 591 K. Applying magnetic field on ErFe_2 induces canting in moments of Er sublattice. We calculated the canting angles at 0.64 T_comp at which they have the same magnetic state. The Fe-Er interaction plays the biggest role in increasing the magnetic and consequently the total entropy by increasing the magnetic field. Using the values of bulk and shear moduli, we calculated θ_D which equals 258.24 K. Using the calculated DOS at E_F , the electronic heat capacity coefficient γ_e was found to be 27 mJ⁄mole.K^2. For an applied magnetic field change up to 6 T, we found that the highest value of the direct magnetocaloric potential near Curie temperature is around 0.23 J/mole.K, while the highest value of the inverse magnetocaloric potential near compensation temperature is around 0.13 J/mole.K. We predict that any compound without compensation temperature like DyFe_2 has no an inverse MCE. The adiabatic temperature change increases by around 0.5 k/T and the maximum value reaches 3 K, for an applied magnetic field change up to 6 T. The two-sublattice molecular field model succeeded to explain the thermomagnetic properties for ErFe_2.