Following our previous work on the magnetocaloric compounds FeMnAs_xP1−x, we obtain thermomagnetic properties for the barocaloric antiperovskite Mn₃GaN, which has been investigated in recent years in view of its thermal response under pressure cycling. Its structure displays canting of spins and a volume dilation in the antiferromagnetic (AFM) transition, related to magnetoelastic coupling. A random-phase-approximation (RPA) Green function theoretical treatment is applied to a two-exchange parameter Heisenberg model, and the canting of the spins orientation in the (111) planes of the structure is considered in the model. The observed first-order AFM phase transitions are reproduced by the introduction of a biquadratic spin term in the Hamiltonian, coupled to the volume dilation in the transition. The model is able to predict a greater stability for the canted spin structure as compared with conventional AFM, if the magnitudes of Mn magnetic moments in these structures are taken from the literature. The calculations of quantities of interest for barocaloric applications reproduce quite well the available data on temperature changes and latent heat under pressure cycling, at adiabatic and isothermal conditions, respectively.

中文翻译：

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Mn3GaN中气压热效应的绿色函数处理

继我们之前对磁热化合物 FeMnAs 的研究之后_X磷1-X, 我们获得了气压抗钙钛矿 Mn _{3的热磁性质}GaN，近年来已针对其在压力循环下的热响应进行了研究。其结构显示自旋倾斜和反铁磁 (AFM) 跃迁中的体积膨胀，这与磁弹性耦合有关。将随机相位近似 (RPA) 格林函数理论处理应用于双交换参数 Heisenberg 模型，并在模型中考虑结构的 (111) 平面中自旋取向的倾斜。观察到的一阶 AFM 相变通过在哈密顿量中引入双二次自旋项来再现，并与过渡中的体积膨胀相耦合。与传统 AFM 相比，该模型能够预测倾斜自旋结构的更大稳定性，如果这些结构中 Mn 磁矩的大小取自文献。对气压应用感兴趣的量的计算很好地再现了分别在绝热和等温条件下压力循环下的温度变化和潜热的可用数据。