Błoński P, Hafner J
University of Vienna, Faculty of Physics and Center for Computational Materials Science, Sensengasse 8/12, A-1090 Wien, Austria. Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Kraków, Poland.
J Phys Condens Matter. 2014 Jun 25;26(25):256001. doi: 10.1088/0953-8984/26/25/256001. Epub 2014 May 22.
We report on our relativistic density-functional investigations of the properties of transition-metal dimers adsorbed on a graphene monolayer supported by a Cu(1 1 1) substrate, which extends our studies of dimers in the gas-phase and adsorbed on a freestanding graphene layer (Błoński and Hafner 2014 J. Phys.: Condens. Matter 26 146002). The presence of the Cu(1 1 1) substrate enhances the interaction between the dimer and the support. For homoatomic dimers such as Ir2 and Pt2 a flat adsorption geometry is now preferred over an upright geometry, which is stable on a graphene monolayer. The magnetic moment of the dimer is strongly reduced, the magnetic anisotropy is very low-in contrast to the strong anisotropy of free and graphene-supported Ir2 and Pt2 dimers. For heteroatomic IrCo and PtCo dimers the upright geometry with the Co atom located in a sixfold hollow of the graphene layer is preserved, but the stronger interaction with the support leads to a further enhancement of the large magnetic anisotropy energy of IrCo to 0.2 eV/dimer, while that of PtCo is reduced. The mechanism determining the magnetic anisotropy is discussed in relation to the electronic structure of the dimers.
我们报告了关于吸附在由Cu(1 1 1)衬底支撑的石墨烯单层上的过渡金属二聚体性质的相对论密度泛函研究，这扩展了我们对气相中二聚体以及吸附在独立石墨烯层上的二聚体的研究（Błoński和Hafner，2014年，《物理学报：凝聚态物质》26卷，146002）。Cu(1 1 1)衬底的存在增强了二聚体与支撑体之间的相互作用。对于诸如Ir₂和Pt₂等同原子二聚体，现在平面吸附几何结构比直立几何结构更受青睐，而直立几何结构在石墨烯单层上是稳定的。二聚体的磁矩大幅降低，磁各向异性非常低——这与自由的以及石墨烯支撑的Ir₂和Pt₂二聚体的强各向异性形成对比。对于异原子IrCo和PtCo二聚体，Co原子位于石墨烯层六重空穴位的直立几何结构得以保留，但与支撑体更强的相互作用导致IrCo大磁各向异性能量进一步增强至0.2 eV/二聚体，而PtCo的磁各向异性能量则降低。结合二聚体的电子结构讨论了决定磁各向异性的机制。
