Instituto de Física Armando Dias Tavares, Universidade do Estado do Rio de Janeiro-UERJ, Rio de Janeiro, RJ, Brazil.
J Phys Condens Matter. 2010 Dec 8;22(48):486008. doi: 10.1088/0953-8984/22/48/486008. Epub 2010 Nov 18.
In this work the magnetocaloric effect is theoretically investigated considering a microscopic model Hamiltonian, which describes a magnetic system formed by two sublattices of different magnetic ions coupled by exchange and magnetoelastic interactions. We analyze systematically several profiles of the ferrimagnetic arrangements that were studied earlier without the magnetoelastic interaction. The influence of changing the magnetoelastic parameters on the magnetization, isothermal entropy change and adiabatic temperature change curves are investigated. Depending on the model parameters, the magnetic system shows a first-order magnetic phase transition leading to high direct and inverse magnetocaloric effect, besides two simultaneous first-order magnetic phase transitions which were predicted. A constant ΔS(T) = 0.4 J mol(-1) K(-1) is obtained in the simulated system in a temperature interval of 50 K, around 110 K.
在这项工作中，我们从微观模型哈密顿量出发，理论研究了磁热效应，该模型哈密顿量描述了由两个不同磁性离子亚晶格组成的磁系统，它们通过交换和磁弹相互作用耦合。我们系统地分析了之前没有磁弹相互作用时研究过的几种亚铁磁排列的情况。研究了改变磁弹参数对磁化、等温熵变和绝热温度变化曲线的影响。根据模型参数，磁系统表现出一级磁相变，导致直接和反磁热效应高，此外还预测了两个同时的一级磁相变。在模拟系统中，在 110 K 左右的 50 K 温度区间内，获得了恒定的 ΔS(T) = 0.4 J mol(-1) K(-1)。
