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In this study, the structural and magnetic properties of Si-doped bulk and 2D AlN were systematically investigated by first-principles calculations. Si atoms prefer to substitute Al atoms in both bulk and 2D AlN under N-rich growth conditions. In bulk AlN, Si dopants exhibit a non-magnetic state, uniform distribution, and a strong anisotropic diffusion energy barrier. In contrast to that, Si dopants prefer to form a buckling structure and exhibit a magnetic moment of 1 μB in 2D AlN. At a low Si concentration, Si atoms tend to get together with antiferromagnetic coupling between each other. However, the magnetic coupling among Si atoms changes to ferromagnetic coupling as Si concentration increases, due to the enhanced exchange splitting and delocalized impurity states. At the extreme doping limit, monolayer SiN, along with its analogs GeN and SnN, is a ferromagnetic semiconductor with a large band gap and high Curie temperature. These results indicate that 2D AlN doped by group IV atoms has potential applications in spintronic devices.

Pristine and doped chromium arsenide (CrAs) in six different crystal structures is systematically studied to investigate the structural, magnetic, and optical properties for real applications by first‐principles calculations. First, it is found that the ground‐state structure is an orthorhombic MnP‐type structure with antiferromagnetic spin order. The rocksalt structure is a low‐energy metastable phase and a ferromagnetic metal with high spin polarization at the Fermi level. Second, the NiAs structure and MnP structure have a higher absorption coefficient than other structures in the infrared region and ultraviolet region, respectively. In the visible region, the wurtzite and zincblende structures are more transparent than other structures. At last, the substitution of Cr by Ti and the substitution of As by Te can lead to a phase transition in ground‐state structure and ground‐state magnetic order, respectively. These results can promote the application of the CrAs system into spintronics and optoelectronics.

In this paper, we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations. With the electronic correlation effect considered, we predicted the ground-state structure of CrTe to be NiAs-type (space group P 6 3 /mmc) structure at ambient pressure, consistent with the experimental observation. Moreover, we found two extra meta-stable Cmca and R3m structure which have negative formation enthalpy and stable phonon dispersion at ambient pressure. The Cmca structure is a layered antiferromagnetic metal. The cleaved energy of a single layer is 0.464 J/m 2 , indicating the possible synthesis of CrTe monolayer. R3m structure is a ferromagnetic halfmetal. When the pressure was applied, the ground-state structure of CrTe transitioned from P 6 3 /mmc to R3m, then to F m3m structure at a pressure about 34 and 42 GPa, respectively. We thought these results help to motivate experimental studies the CrTe compounds in the application of spintronics.