Abstract Pseudobinary Gd5(Si,Ge)4 compounds show a giant magnetocaloric effect due to an intriguing structure-magnetism interplay. Here, we report a high resolution transmission electron microscopic study of microstructure in a melt-grown compound of Gd5Si1.5Ge2.5. Electron diffraction showed that mesoscopic microstructure of the compound consists of crystals of a monoclinic structure and two kinds of orthorhombic structure. However, atomic-level imaging revealed a coexistence of mosaic-like nanodomains of these structures in each crystal. The nanodomains have twin-like interfaces along the b axis of the crystal but have semicoherent interfaces along a perpendicular axis due to stacking faults. Such a nanoscale structural heterogeneity is due to covalent bond-controlled phase separation at elevated temperatures. This finding offers insights into phase relations and abnormal magnetic behavior of Gd5(Si,Ge)4 compounds and points out a route of synthesizing bulk nanocomposites via nanoscale phase separation.

中文翻译：

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Gd5Si1.5Ge2.5 中相分离引起的纳米级异质性

摘要 Pseudobinary Gd5(Si,Ge)4 化合物由于有趣的结构-磁性相互作用而表现出巨大的磁热效应。在这里，我们报告了 Gd5Si1.5Ge2.5 熔融生长化合物中微观结构的高分辨率透射电子显微镜研究。电子衍射表明，该化合物的细观微观结构由单斜晶结构和斜方晶结构两种晶体组成。然而，原子级成像揭示了每个晶体中这些结构的马赛克状纳米域的共存。纳米域沿晶体的 b 轴具有孪晶状界面，但由于堆垛层错而沿垂直轴具有半相干界面。这种纳米级结构异质性是由于高温下共价键控制的相分离。