Mean-Field Modeling of Magnetocaloric Effect of Antiferromagnetic Compounds

Antiferromagnetic compounds are known in the literature to present the inverse magnetocaloric effect (MCE). This effect is characterized by the negative adiabatic temperature change $\Delta {T}_S$ of an antiferromagnetic material when submitted to an applied magnetic field. In an isothermal process, a positive entropy change $\Delta {S}_T$ is also expected. More recently, the anisotropic character of antiferromagnetic compounds, due to spin-flop and spin-flip transitions, has been pointed out, highlighting the applicability of the antiferromagnetic compounds in a rotary magnetocaloric device. In this work, we systematically investigated a mean-field model that describes the antiferromagnetic behavior of materials in a multisublattice approach. Our model includes the nearest and next-nearest neighbor exchange interaction, the Zeeman effect, and uniaxial anisotropy energy. We investigated the effect of anisotropy on the spin-flop and spin-flip transitions on the usual and anisotropic MCE. We also demonstrated and verified an area rule for $ - {\rm{\Delta }}{S}_T$ versus T curves that can be used on compounds where the saturation magnetization is magnetic field dependent.