Anisotropic Study of the Magnetocaloric Effect of Nd2Ni2ln Intermetallic

The magnetocaloric effect (MCE) is an intrinsic magnetic property of some materials and can be characterized in terms of the adiabatic temperature variation ΔT or the isothermal magnetic entropy change ΔS. Usually, ΔS is indirectly determined from the magnetization curves (MxT or MxH) or magnetic specific heat according to the Maxwell relation. The Nd2Ni2In compound crystallizes in the tetragonal P4/mbm space group and belongs to the R2T2X family (R = lanthanide or actinide, T = transition metal and X = p-metal). Nd2Ni2In order antiferromagnetic below the temperature of Néel TN = 8 K. In this work, we consider localized magnetism due to 4f electrons with the participation of non-magnetic ligands in the presence of a crystalline electric field (CEF). A model is developed which describes the CEF and magnetic interaction applied to two sublattices, where the magnetic interaction is described by a Hamiltonian who considers the Zeeman and exchange interactions in the molecular field approximation. To adjust S of the Nd2Ni2In intermetallic compound, we implemented to the effective spin model a modulated exchange motivated by the antiferromagnetic-ferromagnetic transition induced to magnetic fields > 0.1 T. Our fitting results of the contribution of Nd2Ni2In to the total −ΔS as a function of temperature were computationally obtained in the [001] crystallographic direction, from the equation of state of magnetization M(H, T) and entropy S (H, T) by diagonalization of the total Hamiltonian (HTot). We obtained a good agreement between the theory and the experiment was using the estimated crystal-field parameters and the exchange integral for Nd2Ni2In.