Vero Khoveto, Borah J P
Department of Physics, National Institute of Technology Nagaland, Chűmoukedima, Nagaland, 797103, India.
Sci Rep. 2024 Aug 16;14(1):19015. doi: 10.1038/s41598-024-69908-0.
The low-temperature phase (LTP) MnBi exhibits remarkable ferromagnetic properties at room temperature. However, below its Curie temperature ( ), a phase transition occurs around 613 K due to diffusion of Mn into interstitial sites, raising concerns about its structural and magnetic properties. Furthermore, the presence of in-plane anisotropy in LTP-MnBi alloy at low temperatures raises concerns about its suitability for use in permanent magnet applications, even at higher temperature. Therefore, this study examines the structural and magnetic properties of pure LTP-MnBi and its successive Ni-doped and Fe-substituted alloys using first-principles study based on density functional theory (DFT). To prevent Mn diffusion into interstitial sites, Ni doping is employed. Additionally, the incorporation of Ni successfully addresses the in-plane anisotropy issue in LTP-MnBi, transforming it into out-of-plane anisotropy. Moreover, we explored the potential advantages of substituting Fe for one of Mn site. This substitution aims to improve the observed dynamical instability in Ni-doped alloy and to further enhanced the magnetocrystalline anisotropy energy (MAE) of the material, resulting in an MAE of 3.21 MJ/m, along with a of 523 K. Therefore, the coexistence of high MAE and moderate in the MnFeBi-Ni alloy presents viable option for its application in permanent magnet technology.
低温相（LTP）的MnBi在室温下表现出显著的铁磁性能。然而，在其居里温度（ ）以下，由于Mn扩散到间隙位置，在约613 K时会发生相变，这引发了对其结构和磁性能的担忧。此外，低温下LTP-MnBi合金中面内各向异性的存在，引发了对其即使在较高温度下用于永磁应用适用性的担忧。因此，本研究基于密度泛函理论（DFT），采用第一性原理研究方法，研究了纯LTP-MnBi及其连续的Ni掺杂和Fe替代合金的结构和磁性能。为防止Mn扩散到间隙位置，采用了Ni掺杂。此外，Ni的掺入成功解决了LTP-MnBi中的面内各向异性问题，将其转变为面外各向异性。此外，我们探索了用Fe替代一个Mn位点的潜在优势。这种替代旨在改善在Ni掺杂合金中观察到的动力学不稳定性，并进一步提高材料的磁晶各向异性能（MAE），从而得到3.21 MJ/m的MAE以及523 K的 。因此，MnFeBi-Ni合金中高MAE和适度 的共存为其在永磁技术中的应用提供了可行选择。
