Structure and magnetism of ferromagnetic nanodot arrays made using nanopatterns on N-adsorbed Cu surfaces

当表面被0.3 ML的N覆盖时，尺寸为5x 5 nm^2的Cu（001）-c（2x2）N的正方形补丁规则地排列为正方形晶格图案。通过在该表面上沉积磁性过渡金属，我们可以制备正方形排列的磁性点阵列。我们研究了纳米图案和纳米点的形成机制及其磁性，在0.3ML氮原子的邻位（001）面上<100>，我们可以形成由单原子台阶隔开的一维正方形氮原子吸附块阵列。在此表面上沉积1-2 ML的Co，制成一维Co点阵列，在超高真空下用磁光克尔旋转法测量了Co点的磁化曲线。测量了Co纳米点阵列的软X射线吸收谱和磁性圆极化率，发现Co纳米点阵列具有平行于台阶边缘的单轴磁各向异性，而Cu（001）表面上的Co纳米点阵列具有四倍的磁各向异性。氮的K边吸收谱表明氮与Co原子成键。CoL 2，3的二向色性随Co的平均厚度的变化而变化，随着Co的平均厚度的减小，轨道磁矩增加.在部分吸附氮的Cu（001）表面上，用光电子能谱观察到晶格应变引起的表面电子结构的变化.结果与第一性原理计算结果一致。用XPS和STM研究了该体系中氮在Co点上的偏聚，认为是由于岛的形成引起的晶格应变所致。

When the surfaces is covered by 0.3 ML of N on the flat surface, square patches of Cu(001)-c(2x2)N with the size of 5x5 nm^2 are arranged regularly as a square lattice pattern. By depositing magnetic transition metals on this surface, we can prepare a magnetic dot array of a square arrangement. We studied the mechanisms of the nanopattern and nanodot formations, and their magnetic properties.On a vicinal (001) surface to <100> with 0.3 ML nitrogen, we can form one-dimensional array of square N-adsorbed patches separated by monatomic steps. On this surface, one-dimensional array of Co dots are made by depositing 1-2 ML Co. We measured the magnetization curves using magneto-optical Kerr rotation method in ultra high vaccum. Uni-axial magnetic anisotropy parallel to the step edge was found on this sample while the anisotropy is fourfold in the Co films on a flat Cu(001) surface.We measured soft X-ray absorption spectra and magnetic circular dichronism on the Co nanodot array. The observed nitrogen K-edge adsorption spectra indicate that the nitrogen is bonding to Co atoms. The dichroism of Co L2,3 was observed as a function of averaged thickness of Co. With decreasing it, the orbital magnetic moment increases.The change of the surface electronic structures due to the lattice strain was observed using photoemission spectroscopy on the partially nitrogen adsorbed Cu(001) surfaces. The results are consistent with the first-principles calculations. The segregation of nitrogen on Co dots in this system was found using XPS and STM, and is attributed to the lattice strain due to the island formation.