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SmCo12磁能积大，是当前备受关注的一种极具应用潜力的高温永磁体，但该体系普遍存在的ThMn12型晶体结构面临严峻的稳定性挑战，严重制约其实际工程应用。探索兼具稳定性和优良磁性能的SmCo12新结构是突破这一瓶颈的关键。本文采用局域粒子群优化算法结合第一性原理计算，系统探索了SmCo12体系的亚稳相。理论计算发现了一种六方相结构（空间群 $P \overline{3} 1 m$），其形成能较传统ThMn12型SmCo12低90 meV/atom。声子谱和分子动力学模拟也证实其具有动力学和热力学稳定性。此外，理论预测六方相SmCo12结构表现出非常优异的磁性能，最大磁能积、各向异性场以及居里温度可达54.56 MGOe、15.01 MA/m以及1180 K。本文新发现的六方相SmCo12为解决ThMn12型结构的稳定性难题提供了新方向。SmCo12, with its large magnetic energy product, is a highly promising high-temperature permanent magnet that has attracted significant attention. However, the widespread ThMn12-type crystal structure in this system faces serious stability issues, which significantly hinder its practical engineering applications. Exploring novel SmCo12 structures that combine stability and excellent magnetic properties is crucial for overcoming this bottleneck. In this study, we systematically investigated the metastable phases of the SmCo12 system using a local particle swarm optimization algorithm combined with first-principles calculations. Theoretical calculations revealed a hexagonal phase structure (space group $P \overline{3} 1 m$) with a formation energy 90 meV/atom lower than that of the conventional ThMn12-type SmCo12. Its phonon spectrum shows no imaginary frequencies and its structure remains stable during Nosé-Hoover thermostat simulations at 1200 K, confirming its dynamic stability and thermodynamic stability. The electronic structure reveals this structureexhibits metallic characteristics, with a total magnetic moment as high as 21.81 µB/f.u. and a magnetocrystalline anisotropy constant up to 11.10 MJ/m3, significantly surpassing those of similar high-cobalt-content Sm-Co systems. Furthermore, theoretical predictions indicate that the hexagonal phase SmCo12 structure exhibits exceptionally outstanding magnetic properties, with maximum energy product, anisotropy field, and Curie temperature reaching 54.56 MGOe, 15.01 MA/m, and 1180 K, respectively. The newly discovered hexagonal SmCo12 phase provides a novel direction for addressing the stability issues of the ThMn12-type structure.
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Keywords:
- Structure prediction /
- First principles calculations /
- High Curie temperature /
- Rare earth permanent magnets
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