Investigation of epitaxially grown artificial magnetic Skyrmions and Merons

非技术摘要磁skyrmion是自旋纹理的一种有趣结构，其中其拓扑结构不会因自旋的任何平滑变形而改变。 由于这种稳定的拓扑结构，Skyrmions表现出许多奇异和独特的性质，可以用于未来的自旋电子技术。 然而，Skyrmion只存在于特殊类型的材料中，并且通常处于低温和高磁场下，因此很难探索其物理性质。 在这项提案中，PI提出了一种新的方法来合成和研究人工磁性skyrmion，以便skyrmion研究可以在室温下和更广泛的材料中进行。 这种方法也允许搜索其他拓扑主题，如所谓的merons。 这些研究结果不仅有助于我们对磁系统拓扑性质的认识，而且在自旋电子学技术中具有潜在的应用价值。 此外，该研究活动将研究与研究生和本科生的基础教育相结合。技术摘要人工磁性skyrmions将通过分子束外延合成，并使用光电发射电子显微镜进行研究。 具有垂直磁化的单晶磁性薄膜将外延生长，在其上将使用接触荫罩生长磁盘。 通过选择合适的圆盘半径和厚度，可以在圆盘内部形成磁涡旋。 界面的磁耦合将涡旋状态从盘印入底层。 因此，一个人造的skyrmion将形成与垂直磁化包围的漩涡。 通过上下切换周围的磁化强度来控制和切换Skyrmion拓扑磁数。 然后，通过将skyrmion涡旋成像为磁场的函数来探索skyrmion的拓扑性质。 其他拓扑对象，如merons也将被搜索和研究在耦合磁盘中，其中的层间耦合和磁盘厚度比将系统地使用双楔增长变化。 特别是，极性和分歧的meron之间的相关性将被探讨。

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.