Cao Yili, Lin Kun, Khmelevskyi Sergii, Avdeev Maxim, Taddei Keith M, Zhang Qiang, Huang Qingzhen, Li Qiang, Kato Kenichi, Tang Chiu Chung, Gibbs Alexandra, Wang Chin-Wei, Deng Jinxia, Chen Jun, Zhang Hongjie, Xing Xianran
Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
Research Center for Computational Materials Science and Engineering, Vienna University of Technology, Karlplatz 13, A-1040 Vienna, Austria.
Phys Rev Lett. 2021 Jul 30;127(5):055501. doi: 10.1103/PhysRevLett.127.055501.
Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic ordering, is of great practical merit for a wide range of high precision engineering. However, the relatively narrow temperature window of SIV in most materials restricts its potential applications in many critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of R_{2}(Fe,Co)_{17} materials (R=rare Earth). We find that adjusting the Fe-Co content tunes the thermal expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from 3-461 K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra and first-principles calculations reveal the 3d bonding state transition of the Fe-sublattice favors extra lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of the internal molecular field, which can be manipulated to achieve "ultrawide" SIV over broad temperature, composition and magnetic field windows. These findings pave the way for exploiting thermal-expansion-control engineering and related functional materials.
超级因瓦合金（SIV），即由磁有序支撑的金属材料的零热膨胀，对于广泛的高精度工程具有巨大的实际价值。然而，大多数材料中SIV相对较窄的温度窗口限制了其在许多关键领域的潜在应用。在此，我们展示了对一系列R₂(Fe,Co)₁₇材料（R = 稀土）热膨胀的可控设计。我们发现，调整Fe-Co含量可调节热膨胀行为，其优化导致了创纪录的宽温度范围的SIV，在3 - 461 K范围内具有良好的循环稳定性，几乎是目前已知SIV范围的两倍。原位中子衍射、穆斯堡尔谱和第一性原理计算表明，Fe亚晶格的3d键合态转变有利于磁有序时产生额外的晶格应力。另一方面，Co含量会显著增强内部分子场，可对其进行调控以在宽温度、成分和磁场窗口内实现“超宽”SIV。这些发现为开发热膨胀控制工程及相关功能材料铺平了道路。
