Affiliation of Author(s):理学院
Journal:ACTA PHYSICA SINICA
Key Words:first principles Co/h-BN Dzyaloshinsky-Moriya interaction Skyrmion
Abstract: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_alpha-B_beta grid, which is indicated by the analysis of spin charge contour plot and partial density of states of each atom, where alpha and beta 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 (J(i) and d(i)) 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 J(1) has a negative value and plays a major role, J(3) is one order of magnitude smaller than J(1), 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 J(1) and smaller positive J(2). The DMI is not shown in this interface with d(1) and d(2) 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.
ISSN No.:1000-3290
Translation or Not:no
Date of Publication:2018-06-05
Co-author:Huang Can,Li Xiao-Ying,pyf,fjy,Shi Daning,Ma Chun-Lan
Correspondence Author:朱岩,潘燕飞,Zhu Yan