Study On Physical Properties Of Graphene Nanoribbon Based On Monte Carlo Simulation

Graphene has a unique structure and excellent properties,which play an important role in the information,energy,functional materials and other aspects.Its wide applications have an impact on social production and lifestyle.Many of these applications depend on its magnetic property.Therefore,it is of great significance to study theoretically the magnetism of graphene nanoribbon.Based on Monte Carlo simulation,magnetic and thermodynamic properties of graphene nanoribbon and graphene nanoribbon with defects have been studied.The effects of exchange coupling and anisotropy on magnetization,magnetic susceptibility,internal energy,specific heat,blocking temperature and step effect were discussed in detail.For the graphene nanoribbon without defects,it was found that the magnetization curve presented different shapes and saturation magnetizations.As|J|or|J₁|increase,the saturation magnetization of the curve tended to decrease.With the increase of|D₁|or|D₂|,the saturation magnetization of the curve increased.The magnetic susceptibility and specific heat showed peaks on the curves.As|J|or|J₁|increase,the temperatures corresponding to the peaks of the magnetic susceptibility and specific heat moved towards the high temperature.Namely,the blocking temperature increased.However,it moved to low temperature with increasing the anisotropy|D₁|or|D₂|.The internal energy increased with temperature,and there is an inflection point.As|J|or|J₁|increased,the internal energy decreased,while increased with increasing the anisotropy|D₁|or|D₂|.The number of magnetization plateaus of magnetization curve may be different for different parameters.The saturated magnetic field increased in the step effect with the increase of|J|,|J₁|,|D₁|or|D₂|.For the graphene nanoribbon with defects,the defect concentration has an influence on the magnetic and thermodynamic properties of the system.For the same parameters,the magnetization and blocking temperature of the graphene nanoribbon with defects were lower than those of the perfect graphene nanoribbon.When the defect concentration was increased,the magnetization and the internal energy became smaller.The peaks of magnetic susceptibility and the specific moved to low temperature zone.