Investigation of epitaxially grown artificial magnetic Skyrmions and Merons

非技术摘要磁天球是一种有趣的自旋织构结构，它的拓扑结构不随自旋的任何平滑变形而变化。由于这种稳定的拓扑结构，Skyrmions显示出许多奇异和独特的性质，这些性质可以用于未来的自旋电子技术。然而，Skyrmions只存在于特殊类型的材料中，通常处于低温和强磁场中，因此很难对其物理性质进行研究。在这个方案中，PI提出了一种新的方法来合成和研究人造磁天子，这样就可以在室温下在更广泛的材料范围内进行天米子的研究。这种方法还允许搜索其他拓扑主题，如所谓的Merons。这一研究成果不仅有望促进我们对磁系统拓扑性质的认识，而且有望在自旋电子学技术中创造应用潜力。此外，这项研究活动将把研究与研究生和本科生的基础教育结合起来。技术摘要将用分子束外延合成人造磁天子，并用光电子显微镜进行研究。垂直磁化的单晶磁性薄膜将在外延生长，其上的磁盘将使用接触荫罩生长。然后，通过选择合适的圆盘半径和厚度，在圆盘内部形成磁涡流。界面磁耦合将涡旋态从圆盘压印到底层。因此，将形成一个人造的天米子，涡旋被垂直磁化所包围。Skyrmion的拓扑磁数将通过上下切换周围的磁化强度来控制和切换。然后，将通过成像作为磁场函数的天米子涡旋来探索天米子的拓扑性质。还将在耦合盘中搜索和研究其他拓扑体，其中层间耦合和盘厚度比将使用双楔形生长来系统地改变。特别是，我们将探索梅隆的极性和发散度之间的关联。

Non-Technical Abstract A magnetic skyrmion is an interesting structure of the spin texture in which its topology is unchanged against any smooth deformation of the spins. Because of this stable topological structure, skyrmions exhibit many exotic and unique properties that could be used in future spintronic technology. However, skyrmions exist only in special types of materials and usually at low temperature and high magnetic field so that it is difficult to explore their physical properties. In this proposal, the PI proposes a new method to synthesize and study artificial magnetic skyrmions so that skyrmion research can be performed at room temperature and in a much wider range of materials. This method also permits the search of other topological subjects such as the so-called merons. Results of this research are expected to not only advance our knowledge on topological properties of magnetic systems but also to create application potentials in spintronics technology. In addition, this research activity integrates research with basic education at both graduate and undergraduate levels.Technical Abstract Artificial magnetic skyrmions will be synthesized by Molecular Beam Epitaxy and investigated using Photoemission Electron Microscopy. Single crystalline magnetic thin films with perpendicular magnetization will be grown epitxially on top of which magnetic disks will be grown using a contact shadow mask. Magnetic vortices will then be formed inside the disks by choosing appropriate disk radius and thickness. The interfacial magnetic coupling imprints the vortex state from the disk into the underlayer. Therefore an artificial skyrmion will be formed with the vortex surrounded by perpendicular magnetization. The skyrmion topological magnetic number will be controlled and switched by switching the surrounding magnetization up and down. Topological properties of the skyrmions will then be explored by imaging the skyrmion vortex as a function of magnetic field. Other topological objects such as merons will also be searched and investigated in coupled disks in which the interlayer coupling and disk thickness ratio will be systematic varied using double wedge growth. In particular, correlation between polarity and divergence of the meron will be explored.