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首页> 外文期刊>Physical review >Cobalt multilayers on diamond surfaces: An ab initio study
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Cobalt multilayers on diamond surfaces: An ab initio study

机译：钻石表面上的多层钴：从头算研究

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Structural, electronic, and magnetic properties of particular metal-semiconductor hybrid systems are investigated employing spin-density-functional theory within generalized gradient approximation. They consist of one up to six monolayers of cobalt on (111) and (001) surfaces of diamond and are characterized by a very small lattice mismatch of the constituents. For monolayer coverage, the Co atoms adsorb in on top sites on the C(111) surface while they adsorb in symmetric bridge sites on the C(001) surface. Strong covalent bonds arc formed between the Co 3d and C 2p orbitals which saturate all surface dangling bonds in each case. The pd bonds give rise to characteristic bonding and antibonding bands which exhibit no significant spin splitting. As a result, the magnetic moment of the Co atoms on the interface layer is considerably quenched. The magnetic moment of 0.96μ_B per Co atom for one Co adlayer on C(111) turns out to be strongly reduced with respect to 1.76μ_B for the top layer atoms of a Co(0001) surface or 1.87μ_B for a free-standing hexagonal Co monolayer. Further Co adlayers lead to an increase in the magnetization rapidly approaching 1.19μ_B at the Co interface and 1.77μ_B at the Co surface layer. For one Co adlayer on C(001), where each Co atom forms two pd bonds with the substrate, the magnetic moment per Co atom is even reduced to 0.42μ_B, as compared to 1.92μ_B for the top layer atoms of a Co(001) surface or 2.05μ_B for a free-standing cubic Co monolayer. For six Co adlayers on C(001) the magnetic moment turns out to be 0.91μ_B at the interface and 1.92μ_B at the surface layer. For both types of hybrid systems the spin polarization at the Co-C interface depends sensitively on the number of Co adlayers. For several systems it amounts to about 60% at the Fermi level.
机译：利用广义梯度近似中的自旋密度泛函理论研究了特定金属-半导体混合系统的结构，电子和磁性。它们由金刚石的（111）和（001）表面上最多六个单层钴组成，其特征是组分的晶格失配非常小。对于单层覆盖，Co原子吸附在C（111）表面的顶部部位，而它们吸附在C（001）表面的对称桥部位。在Co 3d和C 2p轨道之间形成了牢固的共价键，使每种情况下的所有表面悬空键都饱和。 pd键产生特征性的键合和反键带，这些键带没有明显的自旋分裂。结果，界面层上的Co原子的磁矩被相当大地淬灭。事实证明，相对于Co（0001）表面顶层原子的1.76μ_B或独立六角形的1.87μ_B，C（111）上一个Co附加层的Co磁矩为0.96μB/ B钴单层。进一步的Co附加层导致磁化强度迅速增加，在Co界面处接近1.19μB，在Co表面层处达到1.77μB。对于C（001）上的一个Co附加层，其中每个Co原子与基底形成两个pd键，每个Co原子的磁矩甚至减小到0.42μ_B，而Co（001）顶层原子的磁矩为1.92μ_B ）或2.05μB（对于独立的立方Co单层）。对于C（001）上的六个Co附加层，其磁矩在界面处为0.91μB，在表面层为1.92μB。对于两种类型的混合系统，Co-C界面处的自旋极化都敏感地取决于Co附加层的数量。对于一些系统，在费米水平上约为60％。

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