The phase transitions and associated magnetic entropy changes in the Ni₂Mn_0.70Cu_0.30Ga Heusler alloy have been investigated. A tetragonal crystal structure was observed at room temperature, and upon heating, the material exhibited a partially coupled first order magnetostructural martensitic phase transition near $~$345 K. The coupling of the magnetic and structural phase transitions enhanced during cooling, which was evident in the large variation in the magnetocaloric properties of the material when the measurements were done while heating and cooling. For a field change of 50 kOe, the peak magnetic entropy change obtained while heating was −17 J kg⁻¹K⁻¹. Interestingly, the peak value was −33 J kg⁻¹K⁻¹ when the measurements were done while cooling from 400 K to lower temperatures. The phase transitions were accompanied by sharp anomalies in the electrical resistivity of the material. The experimental results indicated that the magnetocaloric properties of Heusler alloys may be precisely controlled by manipulating the overlap of the first order martensitic and the second order ferromagnetic phase transitions.

已经研究了 Ni ₂ Mn _0.70 Cu _0.30 Ga Heusler 合金中的相变和相关的磁熵变。在室温下观察到四方晶体结构，加热后，材料表现出部分耦合的一级磁结构马氏体相变接近$~$345 K. 冷却过程中磁性相变和结构相变的耦合增强，这在加热和冷却时进行测量时材料的磁热特性的巨大变化中很明显。对于50 kOe 的场变化，加热时获得的峰值磁熵变为-17 J kg ^-1 K ^-1。有趣的是，峰值为 -33 J kg ^-1 K ^-1当测量是在从 400 K 冷却到较低温度的同时进行的。相变伴随着材料电阻率的急剧异常。实验结果表明，可以通过操纵一阶马氏体和二阶铁磁相变的重叠来精确控制赫斯勒合金的磁热性能。