Tuning the magnetocaloric response in half-Heusler/Heusler MnNi1+xSb solid solutions
Tuning the magnetocaloric response in half-Heusler/Heusler MnNi1+xSb solid solutions
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DOI：
10.1103/physrevmaterials.1.075003
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发表时间：
2017-12-14
影响因子：
3.4
通讯作者：
Seshadri, Ram
中科院分区：
文献类型：
--
作者：
Levin, Emily E.;Bocarsly, Joshua D.;Seshadri, Ram
具有大磁热响应的材料与施加磁场时的温度变化有关，在磁制冷和热磁发电中具有重要的应用价值。这种响应的通常度量是重力等温熵变增量S-M。用基于密度泛函理论的磁电子结构计算方法对S-M进行了简单的模拟，结果表明半Heusler化合物MnNiSb比相应的Heusler化合物MnNi2Sb具有更好的磁热效应。在这一观察的指导下，我们对MnNi1+xSb(x=0，0.25，0.5，0.75和1.0)进行了研究，以评估相关的结构和磁性。密度泛函稳定性计算表明，Ni的加成发生在半Heusler结构中对称不同的Ni位，并支持用同步加速器x射线衍射观察到的半Heusler端元和Heusler端元之间的均匀固溶体。饱和磁化强度在x=0.5时出现极大值，居里温度随x的增加而系统地降低，在H=5T的最大磁场变化时，S-M的幅度单调地从半赫斯勒化合物的-2.93J kg(-1)K-1减小到海斯勒化合物的-1.35J kg(-1)K-1。在x=0.75时，磁相变同时展宽导致制冷剂容量达到最大值。该系统的居里温度在350K至750K之间高度可调，是通过热磁发电回收低品位废热的理想选择。德尔塔S-M随x的增加可能扩展到其他MnNi(2)Z Heusler系统，这些系统目前正在研究中，用于磁热制冷应用。
Materials with a large magnetocaloric response are associated with a temperature change upon the application of a magnetic field and are of interest for applications in magnetic refrigeration and thermomagnetic power generation. The usual metric of this response is the gravimetric isothermal entropy change Delta S-M. The use of a simple proxy for the Delta S-M that is based on density functional theory (DFT) calculations of themagnetic electronic structure suggests that half-Heusler MnNiSb should be a better magnetocaloric than the corresponding Heusler compound MnNi2Sb. Guided by this observation, we present a study of MnNi1+xSb (x = 0, 0.25, 0.5, 0.75, and 1.0) to evaluate relevant structural and magnetic properties. DFT stability calculations suggest that the addition of Ni takes place at a symmetrically distinct Ni site in the half-Heusler structure and support the observation using synchrotron x-ray diffraction of a homogeneous solid solution between the half-Heusler and Heusler end members. There is amaximum in the saturationmagnetization at x = 0.5 and the Curie temperature systematically decreases with increasing x. Delta S-M for a maximum magnetic field change of Delta H = 5 T monotonically decreases in magnitude from -2.93 J kg(-1) K-1 in the half-Heusler to -1.35 J kg(-1) K-1 in the Heusler compound. The concurrent broadening of the magnetic transition results in a maximum in the refrigerant capacity at x = 0.75. The Curie temperature of this system is highly tunable between 350 K and 750 K, making it ideal for low grade waste heat recovery via thermomagnetic power generation. The increase in Delta S-M with decreasing x may be extendable to other MnNi(2)Z Heusler systems that are currently under investigation for use in magnetocaloric refrigeration applications.