摘要
用密度泛函理论的第一性原理计算程序VASP在广义布洛赫条件下计算了Co/h-BN反方向的自旋螺旋能量与波矢的色散关系E(q)与E(-q).E(q)与E(-q)能量之差反映了Co/h-BN界面上下层之间空间反演对称性破缺引起的Dzyaloshinsky-Moriya相互作用(DMI)的大小.通过海森伯作用(HBI)模型与DMI模型拟合计算值,得到Co原子间各近邻的HBI参数J_1—J_4及DMI参数d_1,d_2.在Co/h-BN中,J_1为负值起完全主导作用,J_3比J_1小一个量级,其他参数接近于0.因此,Co/h-BN的基态是三角反铁磁,而DMI很微弱.根据这种性质,h-BN可以作为其他DMI界面的覆盖层.
Based on density functional theory calculations, we elucidate the atomic and electronic structures of Co atom of hexgonal BN （Co/h-BN）. The interaction between magnetic moments of Co atoms is realized through Co-N_α-B_β grid, which is indicated by the analysis of spin charge contour plot and partial density of states of each atom, where α and β denote the site of B or N atom close to and away from Co atom, respectively. Then the dispersion relations E（q） and E（-q） （q denotes the direction vector of spin spiral） between energy and wave vector of spin spiral in the opposite directions are calculated with generalized Bloch equations. In the incommensurate spin spiral calculations, all the magnetic moments of Co atom are arranged in the same plane that is perpendicular to the Co/h-BN film. The difference between E（q） and E（-q） is caused by the interface of Co/h-BN, where the symmetry of space perpendicular to the film is broken. Moreover, the effective Heisenberg exchange interaction （HBI） and Dzyaloshinsky-Moriya interaction （DMI） parameters between different neighbors （Ji and di） are derived by well fitting the ab initio magnon dispersion E（q） to HBI with DMI model and E（q） - E（-q） to DMI model, respectively. The J1 has a negative value and plays a major role, J3 is one order of magnitude smaller than J1, and other parameters are close to zero. Hence, Co/h-BN is triangular antiferromagnetic material with the q at k point in the first Brillouin zone. However, the spin spiral with the q at M point is only 2 meV larger than the basic state with the only negative J1 and smaller positive J2. The DMI is not shown in this interface with d1 and d2 close to zero. Based on the non DMI character and its stability in air, h-BN can be capped on other DMI interfaces. The reason that the DMI in Co/h-BN is much smaller than in Co/Gra is much larger height between Co and h-BN. It is 0.192 nm for h-BN but it is 0.156 nm for Co/Gra. We may reduce the height to enhance the DMI by other ways, such as adding electrical and magnetic fields in the future.
作者
黄灿
李小影
朱岩
潘燕飞
樊济宇
施大宁
马春兰
Huang Can;Li Xiao-Ying;hu Van;Pan Yan-Fei;Fan Ji-Yu;hi Da-Ning;Ma Chun-Lan(ollege of Science, Nanjing University of Aeronautics and Astronautics, Najing 210006, China;chool of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009, China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第11期191-198,共8页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11204131
11374159)
江苏省高等学校自然科学研究重大项目(批准号:17KJA140001)
江苏省"六大人才高峰"高层次人才项目(批准号:XCL-078)资助的课题~~
