GIANT MAGNETOCALORIC EFFECT OF COMPRESSIBLE ISING AND HEISENBERG LATTICES

摘要

Since the discovery of giant magnetocaloric materials, it has become clear that magnetovolume coupling can lead to a large increase to a material's magnetocaloric effect, and so, to high-performance magnetic refrigerants. A simple and computationally inexpensive approach to gauge magnetovolume effects is via the Bean-Rodbell model, where a Curie temperature dependence on volume is included in the Weiss mean-field model. The thermodynamic properties of giant magnetocaloric materials are described, namely discontinuous magnetization curves and large entropy change values. Moving to a microscopic model is a natural step to better characterize giant magnetocaloric materials. In this work we show how an Ising/Heisenberg-type interaction together with elastic/magnetovolume coupling can be solved by a Monte-Carlo method, reproducing the thermodynamic properties of giant magnetocaloric systems. The low computational cost of this approach and the possibilities of simulating systems using Density Functional Theory calculated magnetic interaction parameters allow the computational study and design of (giant) magnetocaloric materials.