In-situ study of the temperature effects on the magneto-structural transition in the MnCoGe-based magnetocaloric compounds

IF 8.3 1区材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY

Acta Materialia Pub Date : 2025-06-09 DOI:10.1016/j.actamat.2025.121241

Xiaowen Hao , Ying Zhao , Xiaoming Huang , Kang Liu , Binru Zhao , Cuiping Zhang , Jie Ma , Fengjiao Qian , Xuefei Miao , Yafei Kuang , Haile Yan , Zongbin Li , Liang Zuo , Xin Tong , Bo Yang , Qingyong Ren

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Abstract

The first-order magneto-structural transition with large adiabatic magnetic entropy change shows great potential for magnetocaloric refrigeration but is hindered by large thermal and magnetic hysteresis effects, such as in the MM'X alloys (M, M' = 3d transition element, X = Si, Ge). While progress has been made in reducing thermal hysteresis through improved geometric compatibility, the joint effects of thermal and magnetic hysteresis are not well understood, which is a crucial issue in the practical operation of magnetocaloric refrigeration. In this work, we present an in-situ study of the temperature effects on the magnetic-field-driven magneto-structural transition in MnCoGe-based compounds. Our results show that the metamagnetic transition from paramagnetic hexagonal to ferromagnetic orthorhombic structures is more easily driven by an external magnetic field during cooling compared to heating. The magnetization loop exhibits larger hysteresis losses during cooling, while the magneto-structural transition temperature determined from iso-field magnetizations is more affected by the magnetic field. Additionally, the negative thermal expansion behavior displays a more uniform distribution within the entire phase transition temperature window during cooling. In-situ X-ray diffraction measurements and geometric nonlinear theory analysis suggest that those discrepancies during heating and cooling originate from smaller lattice geometric incompatibilities, particularly along the a-axis of the orthorhombic structure. Furthermore, it is found that the transformation stretch tensor eigenvalues exhibit linear behavior, converging towards 1 and indicating improved compatibility, potentially leading to reduced thermal hysteresis effects at lower temperatures. These findings offer insights into magneto-structural transitions and hysteresis behaviors, informing the development of high-performance magnetocaloric materials.

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温度对mncoge基磁热化合物磁结构转变影响的原位研究

具有较大绝热磁熵变化的一阶磁-结构转变显示了磁热制冷的巨大潜力，但受到较大的热磁滞后效应的阻碍，例如在MM‘X合金中（M， M’ = 三维过渡元素，X = Si, Ge）。虽然通过改善几何相容性来减少热滞后已经取得了进展，但热滞后和磁滞后的联合效应还没有得到很好的理解，这是磁热制冷实际操作中的一个关键问题。在这项工作中，我们提出了一项原位研究温度对磁场驱动的mncoge基化合物磁结构转变的影响。我们的研究结果表明，与加热相比，在冷却过程中外部磁场更容易驱动从顺磁六边形结构到铁磁正交体结构的超磁转变。磁化回路在冷却过程中表现出较大的磁滞损失，而由等磁场磁化确定的磁结构转变温度受磁场的影响更大。此外，在冷却过程中，负热膨胀行为在整个相变温度窗内的分布更为均匀。原位x射线衍射测量和几何非线性理论分析表明，加热和冷却过程中的这些差异源于较小的晶格几何不相容，特别是沿正交结构的a轴。此外，发现变换拉伸张量特征值呈现线性行为，趋近于1，表明相容性改善，可能导致较低温度下热滞后效应的减少。这些发现提供了对磁结构转变和磁滞行为的见解，为高性能磁热材料的开发提供了信息。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Acta Materialia 工程技术-材料科学：综合

CiteScore

16.10

自引率

8.50%

发文量

801

审稿时长

53 days

期刊介绍： Acta Materialia serves as a platform for publishing full-length, original papers and commissioned overviews that contribute to a profound understanding of the correlation between the processing, structure, and properties of inorganic materials. The journal seeks papers with high impact potential or those that significantly propel the field forward. The scope includes the atomic and molecular arrangements, chemical and electronic structures, and microstructure of materials, focusing on their mechanical or functional behavior across all length scales, including nanostructures.