First-principles Study Of Several Two-dimensional Ternary Transition Metal Dichalcogenides

In recent years,with the rapid development of science and technology,people's require-ments for electronic devices in high-tech field has become higher and higher,especially in terms of their function and volume.Spintronics materials take advantage of the freedom of electron charge and electron spin,which greatly improves efficiency of data transmission and storage,thus it plays an important role in the new generation of electronic devices.The magnetic half-metal and magnetic semiconductor materials in spintronics are ideal candi-dates for new generation of spintronics devices because of their stable magnetic properties and high spin polarization.In this paper,we used the first-principles calculation package VASP based on density functional theory.We calculated the electronic structures,magnetic properties and mechanical properties of two-dimensional CrAsS₄,MnAsS₄and Mn XSe₄(X=As,Sb)by using projector augmented wave method.The main research contents are as follows:Firstly,we optimized the structure of ferromagnetic and antiferromagnetic states of two-dimensional CrAsS₄,MnAsS₄and Mn XSe₄(X=As,Sb).By comparing the energy,we determine the ground state of two-dimensional CrAsS₄,MnAsS₄and Mn XSe₄(X=As,Sb).Then their stability is determined by phonon spectrum and elastic constant,etc.Secondly,we calculated the electronic properties and magnetic properties of CrAsS₄,MnAsS₄and Mn XSe₄(X=As,Sb).Besides,we studied the energy band,density of states,differential charge density,spin density and the magnetic moment of a single magnetic atom in the primitive cell.We also discussed and analyzed of their possible applications in the field of spintronics.Finally,we observed the variation trend of band gap and the variation of magnetic phase when uniaxial strain was applied to two-dimensional CrAsS₄in different directions,and analyzed the mechanism of magnetic phase changes from the microscopic perspective.In addition,we studied the variation trend of half-metal gap and spin gap and the changes in total magnetic moment and magnetism under biaxial strain of two-dimensional MnAsS₄.We also used Monte Carlo method to simulate the Curie temperature of MnAsS₄.What's more,we calculated the magnetic anisotropy energy and the Curie temperature of two-dimensional Mn XSe₄(X=As,Sb),also calculated the energy band when considering the spin-orbit coupling.