Sm-Co nanoparticles (NPs) are promising candidates for preparing superstable magnets and exchange-coupled nanocomposite magnets with unprecedented magnetic properties. However, the morphology evolution of the NPs remains unclear. Here, single crystalline SmCo_x (x = 4.07, 4.79, 6.94, and 8.61) NPs with dimensions below the critical size of a single magnetic domain were synthesized. These NPs consist of Sm₂Co₇, SmCo₅, and Sm₂Co₁₇ phases with divergent typical morphologies. An evolution model for the different morphological characteristics was proposed based on phase-structure changes and surface-energy calculations using the density functional theory. The results show that these SmCo_4.79 NPs can be well aligned along the easy magnetization axis and exhibit an ultrahigh coercivity of 5.7 T, thus enabling to advance the control of NP morphology and to facilitate their use in superstable or nanocomposite magnets.

Sm-Co纳米粒子（NPs）是制备具有前所未见的磁性的超稳定磁体和交换耦合纳米复合磁体的有希望的候选者。但是，NP的形态演变仍不清楚。在此，合成了尺寸小于单个磁畴临界尺寸的单晶SmCo _x（x = 4.07、4.79、6.94和8.61）NP。这些NP由Sm ₂ Co ₇，SmCo ₅和Sm ₂ Co _17组成具有不同典型形态的相。基于相结构变化和利用密度泛函理论的表面能计算，提出了不同形态特征的演化模型。结果表明，这些SmCo _4.79 NPs可以沿着易磁化轴很好地排列，并具有5​​.7 T的超高矫顽力，因此可以促进NP形态的控制，并促进其在超稳定或纳米复合磁体中的使用。