Tunable Electronic Structure Of Two-dimensional Transition Metal Trihalides

Two-dimensional(2D)monolayer transition metal trihalides MX₃(M=Sc?Ti?V?Cr?Mn?Fe?Co?Ni?Cu?Zn;X=Cl?Br?I)have attracted much attention due to its unique electronic structure and physical properties.MX₃ monolayer is a family with intrinsic ferromagnetism,magnetic anisotropy,high Curie temperature and tunable band gap,which have the potential applications in ultrathin magnetic storage,magneto-optical detector,optoelectronic and spintronic devices.The electronic structure and physical properties of 2D MX₃ materials can be modulated by the interfacial recombination and anion substitution,which provide the theoretical foundation for the practical applications in spintronics and magnetic storage devices.In this dissertation,strain-tunable magnetic anisotropy in 2D Dirac half-metals NiX₃(X=Cl?Br?I),electric polarization related Dirac half-metallicity in 2D Mn₂X₃Y₃(X,Y=Cl?Br?I;X?Y)Janus,and nonvolatile electrical control switching in2D Mn Cl₃/CuInP₂S₆ van der Waals(vd W)heterostructures are investigated systematically by using the density functional theory.The electronic structure of 2D NiX₃ has been calculated.The results show that NiX₃ monolayer is a family of Dirac half-metals with intrinsic ferromagnetism,big half-metallic gap and high carrier mobility,which is ideal material for spintronics.The electronic structure,Curie temperature and magnetic anisotropy energy can be modulated by the biaxial strain.The electronic structure of 2D Mn₂X₃Y₃ Janus has been calculated.The results show that the hybridization intensity of Mn and the halogen atoms on both sides of Mn₂Cl₃I₃ is greatly different due to the large electric polarization,which resulting in an obvious distortion of the spin-polarized Dirac cone.The distorted Dirac cone is repaired by the compression,indicating that strain can improve the orbital distortion induced by the electric polarization.All Mn₂X₃Y₃ Janus monolayer have the in-plane magnetization anisotropy,which is mainly contributed by heavy halogen element(Br and I),and the polarized substitution and biaxial strain will not change the easy magnetization orientation of the system.The electronic structure of 2D Mn Cl₃/CuInP₂S₆ vd W heterostructures has been calculated.The results show that When Mn Cl₃ is combined with CuInP₂S₆ in P?state,the Dirac cones of spin-up channel are destroyed due to the interfacial charge transfer,but the half-metal characteristic is preserved.By contrast,Mn Cl₃ transforms into a magnetic semiconductor upon contacting with CuInP₂S₆ in P?state.We propose a new general approach to achieve nonvolatile electrical control switching in 2D Mn Cl₃/CuInP₂S₆ heterostructure.