Structural And Magnetic Properties Of Copt Clusters Supported On Ni(100) Surface:A Density Functional Theory Investigation

The hard-magnetic alloy clusters, which consist of a combination of 3d metal atoms Fe, Co with a high-spin moment and 5d metal atoms Pt (or 4d metal Rh, Pd) with strong spin-orbit coupling, can exhibit large uniaxial magnetic anisotropy energy (MAE), and consequently are expected to be the promising magnetic recording media for advanced high-density data storage. Although intensive investigations have been recently devoted to their structural information and novel magnetic characters, only fewer studies have addressed the problem of their magnetic anisotropy. It is quite remarkable that very little is still known about the microscopic origin of the MAE in nanoalloys and about the possibility of systematic material optimization that it offers.In this project, by means of the first principle theory (DFT) method and fully relativistic theory including the spin-orbit interaction, the geometrical evolution, spin and orbital moment, as well as the MAE of Con-xPtx (n=1-3; x≤n) clusters would be systematically studied, in designing different structures with either mixed configurations or segregated configurations. In addition, the deposition of small and large size-selected clusters on Ni (100) surfaces will be explored. By varying the cluster size, distribution, and composition of the two elements, we want to tailor the structural morphology and 5d interfaces, in order to obtain the clusters with high structural stability, high magnetic moment, and large uniaxial MAE in free-standing systems, and even a perpendiucular magnetic anisotropy in deposited systems. In the meanwhile, the emphasis would be paid to the issues that how the Pt atoms control the magnetoanisotropic behavior and induce magnetic moments at the 5d interfaces. The magnetic moments and magnetic anisotropy energy (MAE) have been calculated for both bulk and clusters, and the enhanced magnetic moment as well as the enlarged MAE have been identified in clusters.The results are followings:(1)the single atomic deposition tend to occupy the FCC hole site to form Pt-Ni bond and Co-Ni bond; the Co2 and Pt2 dimer pefer to occupy the adjacent FCC hole sites (the first nearest two sites); except for Co3 cluster in which one Co atom is at the bridge site, the rest of the atoms are dominated in the FCC hole sites. (2)with the increasing size of clusters, the stability of the sedimentary system increase, but the adsorption stability of the CoPt cluster reduce as a Pt atom introduced into the clusters. (3)the μspirtCo in Con/Ni(100) systems decrease slightly due to the hybridization between Co-3d and substrate Ni-3d bonds. The μspinCo and μorbCo remain 2.0 μB and 0.15μB respectively and both of which decrease a little with the change of the clusters size but have nothing to do with the adsorption sites; the effect on Co magnetic moment via the spin-orbit coupling of Pt atoms is somewhat smaller than that via the hybridizations between Co and substrate Ni atoms. (4)the easy magnetization axis is parallel to the surface of Ni substrate, as a Pt atom is gradually introduced into the clusters, the MAEs of CoPt clusters increase to 15-20 meV. (5)the oxidation effect on structure and magnetic intensity of CoPt is small, but it will significantly reduce the MAEs of the clusters.