最近复旦大学的修发贤等人发现通过构造二维铁磁材料Fe3GeTe2和反铁磁CrSb的异质结，居里温度能够得到较大的提升，他们将这种现象归因于由近邻效应所产生的界面处CrSb的磁性增强和界面处的铁磁耦合。基于第一性原理计算，我们发现在CrSb(001)薄膜中也产生了类似的表面磁性增强的现象。基于这一现象，我们进行了如下研究：
1、我们使用第一性原理方法对零温下的CrSb体结构的海森堡交换作用系数以及磁化曲线进行了研究。我们基于局域密度近似（local density approximation, LDA）、 PerdewBurke-Ernzerhof （PBE）交换关联函数，使用在实空间中翻转部分磁矩的方法计算了CrSb块材的海森堡交换作用系数，结合蒙特卡罗模拟计算得到了CrSb 块材的磁化曲线和奈尔温度。计算结果表明，基于LDA 计算得出的奈尔温度相比实验测量值（723K）高估了大约24%，而PBE 高估了大约52%。我们通过在PBE基础上采用库仑势修正方法，在Cr原子上加U进行了U-J 范围为0.5-3.0eV的DFT+U 的计算。计算结果表明，当U-J =2.0eV时，在考虑最近邻相互作用下计算得到的奈尔温度为740K，与实验值（723K）较为符合。
2、我们基于第一性原理计算，对薄膜的磁性和磁晶各向异性能进行了研究。计算结果表明，层数为2、4、6、8、10层的薄膜中普遍存在表面磁性增强的现象。通过计算6层薄膜的分层d波态密度，我们对CrSb 薄膜表面磁性增强的原因在进行了讨论。通过对薄膜结构的分析可知，表面Cr原子化学环境与体结构中的Cr 原子是不同的，体结构中Cr 原子存在上下两层的Sb 原子，而表面Cr原子只存在下层的Sb 原子，表面对称性下降，形成了更多的局域的自旋向上的表面态，而自旋向下表面态有所减少，从而导致了表面磁性的增强。我们使用第一性原理计算，通过非自洽方法，改变自旋的量子化轴方向，研究了体结构和(001)方向薄膜的磁晶各向异性能。计算结果表明，当层数降为2层时薄膜具有面内的易轴。当层数为4、6、8、10层时，磁晶各向异性仍保持块体的垂直各向异性。

Recently, Faxian Xiu et al. discovered that by constructing a heterostructure of twodimensional ferromagnetic material Fe3GeTe2 and antiferromagnetic CrSb, the Curie temperature can be greatly increased. The proximity induced magnetism enhancement of CrSb and the ferromagnetic coupling at the interface give rise to the enhancement of Curie temperature of the Fe3GeTe2 film. Based on first-principles calculations, we found that a similar phenomenon of surface magnetic enhancement has also occurred in CrSb(001) films. 

Based on this phenomenon, we investigate the single crystal CrSb and CrSb(001) films, the details are as follows:

1. By using the first-principles method, we investigate the Heisenberg exchange interaction coefficients and magnetization curve of the bulk CrSb at zero temperature. Based on local density approximation (LDA), Perdew-Burke-Ernzerhof (PBE) exchange correlation functional, we use the method of flipping part of the magnetic moments in real space to calculate the Heisenberg exchange interaction coefficients of CrSb. The Monte Carlo method is applied to calculate the magnetization curve and Neel temperature of CrSb. The results show that the Neel temperature calculated based on LDA is overestimated by approximately 24% compared to the Neel temperature (723K) found in experiment, while PBE is overestimated by approximately 52%. By applying
the Hubbard correction to the PBE funcional with an effective U of 2.0eV for the Cr d states results in a Neel temperature of 740K, which is close to the experimental value (723K). 

2. Based on first-principles calculations, the magnetic and magnetocrystalline anisotropy properties of the CrSb films are studied. The calculation results show that the phenomenon of surface magnetism enhancement generally exists in the 2-10 layers. We discussed the reason for the enhancement of the magnetism of Cr at the surface of CrSb films, and calculated the layerresolved d-wave charge density of the 6-layer film. The environment of Cr atoms on the surface is different from the Cr atoms in bulk. Cr atoms are sandwiched between two layers of Sb atoms in bulk. The Sb atoms above the Cr atoms on the surface disappeared, resulting in a symmetry break, and thus the states become more localized. The number of local spin-up surface states increases, and the number of spin-down surface states decreases, resulting in an enhancement of surface magnetism. Using first-principles calculations, we changed the direction of the spin quantization axis through a non-self-consistent method to study the magnetocrystalline anisotropy of the 2-10 layers. The calculation results show that the two-layer CrSb (001) film has an in-plane easy axis. When the number of layers is 4-10, the magnetocrystalline anisotropy of the CrSb thin film is basically the same as that of the bulk material. When the number of layers is 4-10, the magnetocrystalline anisotropy still maintains the perpendicular anisotropy of the bulk.