Mn掺杂MoSe_(2)及相关异质结的半金属铁磁性

Half-metallic ferromagnetic properties of Mn-doped MoSe_(2) and its heterostructure

本文用第一性原理方法研究了过渡金属Mn掺杂MoSe_(2)单层(Mo_(0.75)Mn_(0.25)Se_(2))的晶体结构、电子结构和磁性质,发现上下自旋电子分别呈现金属特性和绝缘特性,即体系具有半金属性.结合轨道态密度图,发现两个邻近Mn原子之间通过Mo4d和Se 4p轨道耦合.在广义布洛赫条件下,计算了单层Mo_(0.75)Mn_(0.25)Se_(2)的自旋螺旋能量与波矢的色散关系,通过海森堡相互作用(HBI)模型拟合计算值得到Mn原子间各种邻近的HBI参数J_(2)(i=1,2,3,4),发现虽然第一近邻交换耦合系数J_(2)起主导作用,但J_(2)的作用不可忽略.鉴于单层Mo_(0.75)Mn_(0.25)Se_(2)属于易氧化的二维金属材料,而单层MoSe_(2)具有绝缘性质,我们构建了异质结MoSe_(2)/Mo_(0.75)Mn_(0.25)Se_(2)/MoSe_(2),计算结果表明异质结两侧的MoSe_(2)可有效保护中间层Mo_(0.75)Mn_(0.25)Se_(2)的半金属铁磁性.该研究可深化对二维半金属铁磁性产生机制的理解,为设计稳定的二维半金属铁磁性材料提供普适方法.

We use the first-principle method to investigate the crystal structure,electronic structure,and magnetic properties of a Mn-doped MoSe_(2)monolayer(Mo_(0.75)Mn_(0.25)Se_(2)).The spin-up electrons exhibit metallic properties,whereas the spin-down electrons exhibit insulating properties,indicating the half-metallic properties of Mo_(0.75)Mn_(0.25)Se_(2).The density of states shows a strong coupling between dopant Mn 3d orbitals via the Mo 4d and Se 4p states.We investigate the dispersion relation of the spin-spiral energy E(q)and the wave vector q for Mo_(0.75)Mn_(0.25)Se_(2)under the generalized Bloch condition.The exchange coupling coefficient J_(2)(i=1,2,3,and 4)is obtained using the Heisenberg interaction model.The nextnearest-neighbor interaction exchange coupling coefficient J_(2)is non-negligible,although the first nearest neighbor,J_(2),plays the most important role in the interaction between atoms.Because Mo_(0.75)Mn_(0.25)Se_(2)is a two-dimensional(2D)metal material that can easily undergo oxidation,we use insulating MoSe_(2)to fabricate a MoSe_(2)/Mo_(0.75)Mn_(0.25)Se_(2)/MoSe_(2)heterostructure.First-principle calculations results show that the half-metallic ferromagnetic properties of Mo_(0.75)Mn_(0.25)Se_(2)can be protected very well in the heterostructure.The findings of this study can promote the understanding of the mechanism of 2D half-metallic ferromagnetic properties and provide a general method for designing materials that show such properties with stability.