Driving The Magnetic Phase Transition Of Graphene Nanoribbons By Fluctuation Field And Doping

Graphene is a new type of two-dimensional material with a layer of carbon atoms arranged in a honeycomb lattice.It is a zero-band gap semiconductor.Despite its short history,it has shown a wealth of new physics and potential applications,Graphene nanoribbons have received extensive attention due to their unique quantum confinement and interference properties.Because edge shape is different,the most common graphene nanoribbons have two different kinds of edge zigzag graphene nanoribbons(ZGNRS)or armchair graphene nanoribbons(AGNRS).The edge of limited zigzag graphene nanoribbons will generate strong local magnetic moment.In recent experiments,it has been reported that by increasing the width of graphene nanoribbon at room temperature,the system realized the phase transition from the AFCE to the FMCE.In general,zigzag-graphene has thermal fluctuation and quantum fluctuation at finite temperature.The key to making microelectronic devices is to regulate the magnetism of small graphene.In this paper,the magnetic properties of graphene are studied by the self-consistent mean field method and TB model.In recent years,many theoretical suggestions have been put forward in the induction of magnetic properties,including using strain,carrier doping,atomic defects,grain boundary,vacancies,hydrogenation adsorption,etc.However,due to the complexity of the experimental environment,it is difficult to prepare perfect graphene,so some researches about graphene cannot be carried out.Monolayer graphene is a two-dimensional crystal.Due to the thermodynamic instability of two-dimensional materials,its surface is uneven and fluctuates(it can be considered that the stable existence of two-dimensional materials lies in the surface fluctuation).On this basis,it is predicted that artificial addition of fluctuation field may affect the boundary magnetism of graphene.The research theory is based on hexagonal lattice graphene nanoribbons with zigzag boundary.By artificially adding fluctuation field on single layer graphene,Hubbard model is tightly bound by single track and self-consistent average field method is used to reveal the influence of fluctuation field intensity,the width of graphene nanoribbons and doping degree on the magnetic properties.By artificially generating the fluctuation field on a single-layer graphene,we theoretically demonstrate how the fluctuation amplitude controls the magnetic behaviors of graphene system.It is proven that,with increasing fluctuation amplitude gradually,the magnetic correlated two edges presents two typical oscillation behaviors between the antiferromagnetic and the ferromagnetic statedepending on the nanoribbon width and doping concentration,and then reaches the ground state of paramagnetism as further increasing the fluctuation amplitude.These findings not only reveal the influence of fluctuation on the intrinsic magnetic behaviors of nanoscale graphene ribbons,but also demonstrate the effective control by external architecture that could be realized by artificial fabrication.