Structural, Electronic And Magnetic Properties Of Co_n-xMn_x(n=0-9, X=0-9) Clusters For Density Functional Calculations

The binary-elemental clusters, especially for bimetal clusters containing magnetic element, have attracted extensively attention in nanomaterial research fields during the past decades. By varying the cluster size and the composition, the optical, catalytic, magnetic properties of these materials can be tailored with our aimed purposes. Furthermore, as non-magnetic element alloyed with strong magnetic element forming bimetal clusters, it would induces definite magnetic moment on non-magnetic elemental atoms, which would results in particularly magnetic behavior that does not exhibit in single-component clusters. Thus, it is important and instructive to perform the comprehensive studies on bimetal clusters, and the following investigation would be beneficial to understand their mechanic characteristic and their promising applications.The low-dimensional CoMn materials have a wide range of applications in magnet-optical recording and high-density magnetic storage, since cobalt is a typical ferromagnetic element, and additionally manganese shows the biggest magnet among 3d transition metals. As for CoMn cluster, experiment studies have found that the average magnetic moments of CoMn clusters increase with the Mn concentration. That is contrary to the bulk Mn_xCo_1-x alloys, in which the presence of manganese leads to a decrease of the mean-per-atom moment. The enhancement moment of CoMn clusters with manganese doping are independent from the size and composition. On the theoretical side, the small clusters with less than 5 atoms, clusters with single atom doping, and structures based on the icosahedral cobalt clusters have been calculated. As a whole, the structure evolution, electronic and magnetic properties of CoMn cluster what our thesis focuses on have not been studied systematically.In this article, by using a fully self-consistent density-functional-theory (DFT) the structure evolution, electronic and magnetic properties of Co_n-xMn_x(n=0-9, x=0-9) clusters are investigated. In the first place, a universal review including the history and present on the cluster is given progressively. The density functional theory as well as the software package which are the theoretical foundation and computational implementation refer to this thesis are introduced in the second section. In the impending part, the details of our work are displayed. All possible geometrical configurations and alternate positions are treated as the initial structures, and then the magnetic properties and the relationship between magnet and components have been analyzed. The detail calculation indicates that Co and Mn atoms tend to mix in structures to maximize stronger Co-Mn bonds. The size, local structural environment, and Mn doping concentration have less effect on Co and Mn atomic magnetic moment, but are sensitive to the magnetic ordering of these atoms. CoMn clusters of low Mn concentration usually represent ferromagnetic coupling and nearly 2μ_B enhancement for one Mn substitutes, whereas, intense antiferromagnetic coupling exists in high Mn doping.