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.
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.
