Study On Electromagnetic Properties Of Two Dimensional Chromium Spintronics Materials

With the continuous improvement of integrated circuit manufacturing technology,its size has been reduced to the nanometer range.At this size level,quantum effects have a certain impact on the reliability,power consumption and other performance of devices.According to the prediction of Moore’s law,integrated circuits have faced great challenges.With the discovery of two-dimensional material graphene,it points out a new direction for the existing bottleneck of integrated circuits in the"Post-Moore".Due to the low dimensional characteristics of two-dimensional materials,they show rich and excellent physical properties such as electricity,magnetism,mechanics and optics.Ferromagnetism is widely used in information storage,logic devices and data processing.However,at present,in most studies,the long-range ordered magnetic state of two-dimensional magnetic materials is usually strongly inhibited in a limited temperature due to thermal fluctuations,resulting in their inability to maintain ferromagnetism at room temperature.Therefore,it is of great research significance to realize the ferromagnetic order and regulation of two-dimensional magnetic materials at room temperature.Based on the density functional theory and the first principle calculation,this paper theoretically studies the electromagnetic properties of two-dimensional chromides and their derivatives and the feasibility of their application in spintronics.The main research contents are as follows:（1）The regulation of edge modification on the electromagnetic properties of the two-dimensional CrSe monolayer was studied.Firstly,it is proved that the two-dimensional CrSe monolayer has good stability by phonon spectrum and molecular dynamics calculation.By calculating its young’s modulus,it is proved that the two-dimensional CrSe monolayer has certain flexibility from the perspective of mechanical properties.Secondly,the structure of the two-dimensional CrSe monolayer and its edge modified structures are analyzed and studied.The calculation results show that the two-dimensional CrSe monolayer is ferromagnetic metal,and when its Cr atoms are modified unilaterally by-F,-H and-O groups,the electromagnetic properties of the two-dimensional CrSe monolayer derivatives are transformed into ferromagnetic half-metal.Their Curie temperatures are calculated by Monte-Carlo simulation.It is found that their Curie temperatures are 530K,530K and 450K respectively,which have reached the level of room temperature.At the same time,when both sides of the two-dimensional CrSe monolayer are modified by chemical groups（-H,-O）,the properties also change to ferromagnetic half-metal,and their Curie temperatures are 220K and 120K respectively.Finally,their magnetic anisotropy is analyzed by spin orbit coupling calculation,and its change process with azimuth is studied.It is found that when Cr atom is unilaterally modified by-O group and the azimuth is 90°,the effect of magnetic anisotropy is the best,up to 0.85me V/atom.Therefore,it shows that edge modification is of great significance for regulating the electromagnetic properties of the two-dimensional CrSe monolayer and increasing Curie temperature.（2）The effects of doping and edge modification on the electromagnetic properties of the two-dimensional Cr₃C₂ monolayer were discussed.Firstly,it is proved that the two-dimensional Cr₃C₂ monolayer has good stability from the perspective of phonon spectrum and molecular dynamics.The electromagnetic properties of the two-dimensional Cr₃C₂ monolayer are studied by using the first-principles calculations.The results show that the two-dimensional Cr₃C₂monolayer is ferromagnetic metal.Secondly,by doping,one layer of C atoms in the two-dimensional Cr₃C₂ monolayer is replaced by N atoms to form the structure of the two-dimensional Cr₃CN monolayer.It is found that its electromagnetic property is also ferromagnetic metal,and it shows stronger ferromagnetic coupling than the two-dimensional Cr₃C₂ monolayer.Finally,because MXenes can not avoid mixing with external chemical functional groups in the actual stripping process,the chemical functional groups-F,-O,-OH are used to modify the edges of them,and their electromagnetic properties and Curie temperature after edge modification are studied.From the research results,the two-dimensional Cr₃C₂F₂monolayer,the two-dimensional Cr₃C₂（OH）₂ monolayer and the two-dimensional Cr₃CNO₂monolayer are transformed from ferromagnetic metal to ferromagnetic half-metal by edge modification,and their Curie temperatures are 650K,760K and 600K respectively by Monte-Carlo simulation.In conclusion,this chapter realizes room temperature two-dimensional ferromagnetic half-metal materials by doping and edge modification,which provides theoretical support for the preparation of spintronic devices.