Abstract

The magnetic and magnetocaloric properties of Heusler Ni_2 + xMn_1 – xGa alloys (x = 0.16, 0.18, and 0.3) have been studied using a model based on the Malygin theory of smeared phase transitions, the Bean–Rodbell theory of first-order phase transitions, and the mean-field theory. The temperature dependences of strain, magnetization, and isothermal change in entropy of these alloys have been analyzed. It is shown that the largest change in the magnetic entropy is observed in a Ni_2.18Mn_0.82Ga alloy, in which the martensitic transition is accompanied by a change in the magnetic ordering. The smallest change in the entropy is observed in a Ni_2.3Mn_0.7Ga alloy, which exhibits the magnetocaloric effect in a martensitic phase with a change in the magnetic ordering. However, the refrigeration capacity of this alloy is twice as high as that of the other considered compositions.

中文翻译：

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Heusler Ni-Mn-Ga合金的磁和磁热性质的理论研究

摘要

Heusler Ni _{2 +  x} Mn _{1-  x} Ga合金（x = 0.16、0.18和0.3）的磁和磁热性质已使用基于涂相转变的Malygin理论（首先是Bean-Rodbell理论）的模型进行了研究。阶相变和均场理论。分析了这些合金的应变，磁化强度和熵的等温变化与温度的关系。结果表明，在Ni _2.18 Mn _0.82 Ga合金中观察到最大的磁熵变，其中马氏体转变伴随着磁有序的变化。在Ni _2.3 Mn _0.7中观察到熵的最小变化Ga合金，在马氏体相中表现出磁热效应，并且磁性顺序发生变化。但是，这种合金的致冷能力是其他被认为是成分的致冷能力的两倍。