First-principles Investigation Of Magnetism About Mn-based Heusler Alloy And Composite Structure Based On Graphene

In recent years,with the explosive growth of technology and gradual advancement of research techniques,more and more new functional materials have been found.Among them,the half-metallic materials have the special electronic structure?100%spin polarization?,which can be well applied to the spintronic devices.The nanomaterials of graphene own abundant physical characteristics,and modified graphene materials can be well used in the application fields such as detection system.In this paper,we have investigated the effect of doping Cr on the electronic structure and magnetism of Mn₂CoAl Heusler alloy based on density functional theory.Besides the composite structure of Ti atom adsorbed on graphene has been calculated.The specific research work and results are summarized as follows:1.The electronic structure and magnetic property of Mn₂Co_1-xCr_xAl?x=0.25,0.5,0.75?have been investigated based on density functional theory calculations.The results indicate that Mn₂CoAl has a very high requirement for occupancy,and a small amount of doping will destroy the original electronic structure and lose the characteristics of zero bandgap magnetic semiconductors.When doped with a small amount of Cr,both Mn₂Co_0.75Cr_0.25Al and Mn₂Co_0.25Cr_0.75Al are half metals with a half-metallic gap of 0.07 eV and 0.08 eV,respectively.2.Due to the disorder should have an influence on the half-metallic character,we further study how the disorder affects the half-metallic property of the Mn₂Co_0.25Cr_0.75Al and Mn₂Co_0.75Cr_0.25Al.The results indicate that Mn₂Co_0.75Cr_0.25Al can maintain the half-metallicity even when the crystal structure is disordered,while the half-metallicity of Mn₂Co_0.25Cr_0.75Al is destroyed once the disorder appears.In addition,for Mn₂Co_0.75Cr_0.25Al,the half-metallic gap of the Cr-Co disordered structure is 0.14 eV,suggesting a great potential to be a good candidate for spintronic application.3?The different adsorption sites of graphene adsorbed transition metal Ti atom are discussed based on the first principle calculation.By comparing the adsorption energy of the composite structures,the most stable adsorption site of Ti atom is the hollow site?H?on graphene layer.The reason of the magnetic generation is explained by analyzing the energy band structure,density of state and partial density of state of the system.Besides,the magnetism is quite obvious in the composite structure of Ti atom adsorbed on graphene,so it is suitable as a magnetic probe to be used in the field of sensor applications.Then,we adjusted the size of the graphene unit cell,and further studied the different concentrations of Ti atom adsorbed on graphene.It was found that the larger the graphene unit cell,the larger the adsorption energy.The height of Ti atom with respect to the graphene layer decreases with the adsorption energy increases.The results will provide theoretical help for the selection of suitable size of probe based on different adsorbed molecules for practical applications.