The DM Interation Of Two-dimensional Non-collinear Antiferromagnetic Materials Study And Regulation

Recent developments in spin-orbital electronics have attracted much attention to chiral spin structures such as skyrmion and domain wall dynamics.These novel physical phenomena can be applied to spintronic memory devices and logic devices,which in turn require the presence of interface Dzyaloshinskii-Moriya interaction（DMI）.DMI is an antisymmetric exchange coupling between adjacent magnetic moments,which exists in a variety of magnetic ordered systems.DMI tends to cause spin skew of magnetic moment,so that the direction of magnetic sequence is no longer strictly parallel or anti-parallel,which is believed to be the source of weak ferromagnetism of antiferromagnets.Usually DMI occur in magnets with non-central symmetry and at the interface between ferromagnets and heavy metals.Magnetic skyrmion is a kind of nanoscale eddy magnetic structure with topological protection.Skyrmion is mainly found in non-chiral magnetic materials with center symmetry and magnetic thin films with broken mirror symmetry.Because it has real space non-banal topologies,magnetic skyrmion exhibit a wealth of novel physical properties,such as the topological Hall effect.It provides a new platform for the study of topological spintronics.On the other hand,because of its small size with small,high stability and easy handling characteristics,the magnetic skyrmion in the future has high density,low power consumption,non-volatile calculations and there are also potential applications in memory devices.First,DMI exists only in non-centrosymmetric systems and plays an important role in the formation of the singular chiral magnetic ground state.However,DMI does not exist in most two-dimensional magnetic materials due to its inherent inversion symmetry.We demonstrate by first-principles calculations that significant DMI can be obtained in Janus monolayers of a series of dialcohols XSe Te（X=Nb,Re）,where the difference between Se and Te on both sides of X breaks the inversion symmetry.It is worth noting that the DMI values of Nb Se Te（1.78me V）and Re Se Te（4.82 me V）are greater than the experimental values of Co/graphene（0.16me V）,and the Curie temperatures of Nb Se Te and Re Se Te monolayer are 1023K and 689K,respectively.Through micromagnetic simulations,we also found that the Re Se Te monolayer can represent the skyrmion state by applying an external magnetic field.Importantly,the skyrmion state can be regulated and controlled under external strain.These findings pave the way for the concept of devices utilizing chiral magnetic structures in specially designed two-dimensional ferromagnetic materials.Secondly,after exploring the strain regulation of Janus single layer XSeTe DMI,we designed a van der Waals heterojunction（MSST/In₂Se₃）.The results show that the magnetic crystal anisotropy of multi-ferromagnetic base heterojunction（MSST/In₂Se₃）changes under the influence of the polarization of ferroelectric substrate In₂Se₃.When the polarization is downward,the magnetic anisotropy energy is 0.148 me V.On the contrary,it is-0.899 me V.At the same time,the strength of DMI also changed.Considering the strongly correlated interaction U,we regulate the magnetic properties of the heterojunction by applying different U values to the heterojunction.We found that the structure with downward polarization has out-of-plane magnetic anisotropy when U=4 e V and simulated the spin magnetic order of the magnetic skyrmion through micromagnetic simulation in this case.We also further studied the influence of external electric field on the spin magnetic order.We found that when the external electric field of-0.5T was applied,the spin magnetic order of the skyrmion disappeared into a ferromagnetic state.Bader charge analysis shows that there is 0.3 electron transfer between the monolayer MSST and donwnwardly polarized In₂Se₃.Based on the above phenomena,it is found that the strength of DMI can be regulated by constructing heterojunction,and the spin magnetic sequence arrangement of materials can be regulated by U value and external electric field.These results are used for non-volatile data encoding and storage with low energy consumption,paving the way for achieving highly tunable topological magnetism in heterogeneous structures.Finally,2D materials with symmetric breaking of intrinsic spatial inversion have been widely concerned.Besides the 1-T Janus structure mentioned above,the 2-H Janus structure is also one of them,and it is very popular in the field of valley electronics.We systematically investigate the MCA and DMI between 2H-XCl Br（X=Os,Ru,Y）monolayer and Gr/XCl Br heterostructure through first-principles.It is found that the interaction strength of DMI between Os Cl Br and Ru Cl Br in 2H phase is higher than that between graphene Co layer by 0.6 me V.In addition,we illustrate that the variation of MAE in plane is mainly due to the interaction between two aspects.For Os Cl Br and Ru Cl Br,it is the orbital coupling between d_xy and d_x2-y2of Br atom,and for YCl Br,it is the orbital coupling between p_x and p_y of Br atom.Then,the energy difference between the antiferromagnetic configuration and the ferromagnetic configuration is calculated,and the difference is 19.56 me V（Os Cl Br）,16.35 me V（Ru Cl Br）,and 5.20 me V（YCl Br）.This means that the ground state of the structure is ferromagnetic.By applying strain to the structure,we can realize the regulation of the exchange coupling coefficient J,and explore the mechanism of the exchange coefficient changing with bond length under strain.By calculating the MAE of Ru Cl Br,we find that the transformation from out of plane to in plane is realized under strain,which also realizes the regulation of strain on the structure MAE.The effect of strain on DMI is analyzed by calculating the energy difference between d^tot and SOC of subatomic component.Finally,we found that it was possible to regulate the DM interaction intensity by using graphene to construct heterojunctions with 2H-XCl Br（X=Os,Ru,Y）monolayers.This shows that we can regulate the magnetic properties and DM interactions of the 2H-XCl Br monolayer by means of strain and the construction of heterojunction,which provides a new way for us to regulate the properties of two-dimensional materials and a new idea for the development of new low-power spintronics devices.