Abstract Heusler-based compounds are a class of important inorganic materials with potential applications in spintronics, solar cell, thermoelectrics, opto-electronics, and so on. Previous studies mainly focus on half-Heusler compounds or full-Heusler compounds. In this work, a class of MCo1.5Sn (M = Ti, Zr, and Hf) compounds, which are named as three-quarter Heusler compounds, has been synthesized. Their formation mechanism, crystal structure, and physical properties have been systematically investigated. Both the high-angle annular dark field images and X-ray refinement confirm that their crystal structures can be viewed as the ordered half-Heusler sublattice with the four empty tetrahedral holes being disorderedly occupied by two extra Co atoms. Electronic structure calculations and experimental results reveal that these compounds are metallic ferromagnets. The magnetic ordering below the Curie temperature greatly affects the electrical transports due to the scattering by spin fluctuations. The three-quarter Heusler compounds have ultralow lattice thermal conductivities comparing with other typical Heusler-based compounds due to the partial occupation of Co at the 4d sites. This work enriches the investigation on the Heusler-based compounds.

中文翻译：

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MCo1.5Sn（M = Ti、Zr 和 Hf）三元化合物：一类四分之三 Heusler 化合物

摘要 Heusler基化合物是一类重要的无机材料，在自旋电子学、太阳能电池、热电、光电子等领域具有潜在应用。以前的研究主要集中在半赫斯勒化合物或全赫斯勒化合物上。在这项工作中，合成了一类 MCo1.5Sn（M = Ti、Zr 和 Hf）化合物，称为四分之三 Heusler 化合物。已经系统地研究了它们的形成机制、晶体结构和物理性质。高角度环形暗场图像和 X 射线精修都证实它们的晶体结构可以被视为有序的半赫斯勒亚晶格，其中四个空的四面体孔被两个额外的 Co 原子无序占据。电子结构计算和实验结果表明这些化合物是金属铁磁体。由于自旋涨落的散射，居里温度以下的磁序极大地影响了电传输。由于在 4d 位点部分占据 Co，四分之三的 Heusler 化合物与其他典型的 Heusler 基化合物相比具有超低晶格热导率。这项工作丰富了对基于 Heusler 的化合物的研究。