The correlation between the covalent bonds and magnetocaloric properties of the Mn2−xFexPyGe1−yMz compounds
The correlation between the covalent bonds and magnetocaloric properties of the Mn2−xFexPyGe1−yMz compounds
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DOI：
10.1063/5.0056190
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发表时间：
2021-10
影响因子：
3.2
通讯作者：
H. R. Zhang;D. Liu;Z. L. Zhang;S. B. Wang;M. Yue;Q. Z. Huang;J. W. Lynn
中科院分区：
文献类型：
--
作者：
H. R. Zhang;D. Liu;Z. L. Zhang;S. B. Wang;M. Yue;Q. Z. Huang;J. W. Lynn
近年来，MnFePGe磁热材料作为磁制冷材料的候选材料受到广泛的研究。MnFePGe的居里温度可以通过改变元素配比或掺杂其他元素调节到室温附近。由于其一阶磁性和结构转变，它产生了很大的熵变，但不幸的是，在相变期间也表现出很大的热滞后，这导致能量损失和较低的制冷能力。本文利用54个Mn 2 − xFexPyGe 1 −yMz（M为金属或非金属掺杂元素）样品，建立了面内共价键与居里温度（TC）、热滞（ΔThys）、两相共存区（ΔTcoex）和熵变（ΔSDSC）之间的关系。利用中子衍射和X射线衍射数据，用最大熵法对六个典型样品进行了详细的电子密度重建。结果表明，面内键长与TC和ΔThys密切相关，而TC、ΔThys、ΔTcoex和ΔSDSC与层间共价键长无显著相关性.此外，我们发现，ΔThys最强烈的相关性时，发生顺磁到铁磁相变的键长的变化，而不是键长的绝对值。这些结果提供了如何控制性能的理解，使有效的方法来调整磁制冷材料的组成，以定制磁热性能的最佳性能。
In recent years, MnFePGe magnetocaloric materials have been widely studied as promising candidates for magnetic refrigeration materials. The Curie temperature of MnFePGe can be adjusted to around room temperature by changing the element ratio or doping with other elements. Due to its first-order magnetic and structural transition, it engenders a large entropy change but unfortunately also exhibits a large thermal hysteresis during the phase transition, which leads to energy loss and lower refrigeration capability. In this paper, we establish a correlation between the in-plane covalent bonding and Curie temperature (TC), thermal hysteresis (ΔThys), two-phase coexistence zone (ΔTcoex), and entropy change (ΔSDSC) using 54 Mn2−xFexPyGe1−yMz (where M is a metallic or nonmetallic doped element) samples with different components. Neutron diffraction and XRD diffraction data and refinements have been employed to allow a detailed electron density reconstruction of six typical samples with the maximum entropy method. We find that the length of the in-plane bonding is closely correlated with the TC and ΔThys, while the TC, ΔThys, ΔTcoex, and ΔSDSC have no significant correlation with the length of the interlayer covalent bond. Moreover, we find that the ΔThys correlates most strongly with the change in the bond length when undergoing the paramagnetic-to-ferromagnetic phase transition rather than the absolute value of the bond length. These results provide an understanding of how to control the properties, enabling effective ways to tune the composition of magnetic refrigeration materials to tailor magnetocaloric properties for optimal performance.