Tian Li-Yun, Gutfleisch Oliver, Eriksson Olle, Vitos Levente
Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, 100 44, Stockholm, Sweden.
Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20, Uppsala, Sweden.
Sci Rep. 2021 Mar 4;11(1):5253. doi: 10.1038/s41598-021-84482-5.
Tetragonal ([Formula: see text]) FeNi is a promising material for high-performance rare-earth-free permanent magnets. Pure tetragonal FeNi is very difficult to synthesize due to its low chemical order-disorder transition temperature ([Formula: see text] K), and thus one must consider alternative non-equilibrium processing routes and alloy design strategies that make the formation of tetragonal FeNi feasible. In this paper, we investigate by density functional theory as implemented in the exact muffin-tin orbitals method whether alloying FeNi with a suitable element can have a positive impact on the phase formation and ordering properties while largely maintaining its attractive intrinsic magnetic properties. We find that small amount of non-magnetic (Al and Ti) or magnetic (Cr and Co) elements increase the order-disorder transition temperature. Adding Mo to the Co-doped system further enhances the ordering temperature while the Curie temperature is decreased only by a few degrees. Our results show that alloying is a viable route to stabilizing the ordered tetragonal phase of FeNi.
四方结构（[化学式：见原文]）的FeNi是一种很有前景的用于高性能无稀土永磁体的材料。由于其化学有序-无序转变温度较低（[化学式：见原文] K），纯四方结构的FeNi很难合成，因此必须考虑替代的非平衡加工路线和合金设计策略，以使四方结构FeNi的形成变得可行。在本文中，我们采用精确 muffin-tin 轨道方法中实现的密度泛函理论来研究，将FeNi与合适的元素合金化是否能在很大程度上保持其有吸引力的固有磁性能的同时，对相形成和有序性能产生积极影响。我们发现少量的非磁性元素（Al和Ti）或磁性元素（Cr和Co）会提高有序-无序转变温度。在Co掺杂体系中添加Mo进一步提高了有序温度，而居里温度仅降低了几度。我们的结果表明，合金化是稳定FeNi有序四方相的可行途径。
