Li Zheng, Zhou Baozeng, Luan Chongbiao
Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electrical and Electronic Engineering, Tianjin University of Technology Tianjin 300384 China
Institute of Fluid Physics, China Academy of Engineering Physics Mianyang Sichuan 621999 China.
RSC Adv. 2019 Nov 4;9(61):35614-35623. doi: 10.1039/c9ra06474e. eCollection 2019 Oct 31.
The recent discovery of intrinsic two-dimensional (2D) ferromagnetism has sparked intense interest due to the potential applications in spintronics. Magnetic anisotropy energy defines the stability of magnetization in a specific direction with respect to the crystal lattice and is an important parameter for nanoscale applications. In this work, using first-principles calculations we predict that 2D NiX (X = Cl, Br, and I) can be a family of intrinsic Dirac half-metals characterized by a band structure with an insulator gap in one spin channel and a Dirac cone in the other. The combination of 100% spin polarization and massless Dirac fermions renders the monolayer NiX a superior candidate material for efficient spin injection and high spin mobility. The NiX is dynamically and thermodynamically stable up to high temperature and the magnetic moment of about 1 per Ni ion is observed with high Curie temperature and large magnetic anisotropy energy. Moreover, detailed calculations of their energetics, atomic structures, and electronic structures under the influence of a biaxial strain have been carried out. The magnetic anisotropy energy also exhibits a strain dependence in monolayer NiX. The hybridization between Ni d and d orbitals gives the largest magnetic anisotropy contribution, whether for the off-plane magnetized NiCl (NiBr) or the in-plane magnetized NiI. The outstanding attributes of monolayer NiX will substantially broaden the applicability of 2D magnetism for a wide range of applications.
近期本征二维铁磁性的发现因其在自旋电子学中的潜在应用引发了强烈兴趣。磁各向异性能量决定了相对于晶格在特定方向上磁化强度的稳定性，是纳米尺度应用中的一个重要参数。在这项工作中，我们使用第一性原理计算预测二维NiX（X = Cl、Br和I）可以是一族本征狄拉克半金属，其能带结构的特征是一个自旋通道中有绝缘能隙，另一个自旋通道中有狄拉克锥。100%的自旋极化和无质量狄拉克费米子的结合使单层NiX成为高效自旋注入和高自旋迁移率的优质候选材料。NiX在高温下具有动力学和热力学稳定性，并且观察到每个Ni离子的磁矩约为1，居里温度高且磁各向异性能量大。此外，还对其在双轴应变影响下的能量学、原子结构和电子结构进行了详细计算。磁各向异性能量在单层NiX中也表现出应变依赖性。无论是对于面外磁化的NiCl（NiBr）还是面内磁化的NiI，Ni d和d轨道之间的杂化都给出了最大的磁各向异性贡献。单层NiX的突出特性将极大地拓宽二维磁性在广泛应用中的适用性。
