ABSTRACT
Skyrmion Crystal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 4 .2 .6 Proposed Skyrmion State in
Ferroelectric Nanocomposites . . . . . . . . . . . . . . . . . . . . 97
4 .3 Experimental Demonstration of Artificial 2D Skyrmion Lattices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 4 .3 .1 Sample Fabrication Process and Hysteresis
Loop Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 .3 .2 The Kerr Microscopy Study of 2D Skyrmion Crystal . . . 102 4 .3 .3 The Magnetic Force Microscopy Study of 2D
Skyrmion Crystal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 4 .3 .4 Photoemission Electron Microscopy Study of
the Epitaxial Artificial Skyrmion . . . . . . . . . . . . . . . . . . 105 4 .3 .5 Scanning Electron Microscopy with a
Polarization Analysis Study of Artificial Skyrmion Crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
With topological charge in real space, skyrmion crystal bears ample interesting phenomena and has great potential for applications. Experimentally, what has impeded its property exploration is the rare material selection as well as the narrow temperature and magnetic field phase diagram. Utilizing dipolar-dipolar interaction, artificial skyrmion crystal was proposed and experimentally realized recently. The artificial skyrmion can completely bypass the need for Dzyaloshinskii-Moriya interaction (DMI), thus significantly enriching the material selections for skyrmions. In addition, an artificial skyrmion crystal has a robust working regime, including room temperature and above, and even without magnetic field. It was found that the created artificial skyrmion crystal exhibits similar static and dynamic behavior to that of skyrmion crystal with DMI. The finding of artificial skyrmions opens a new door to the exploration of the unique fundamental properties of skyrmions. The reported advance marks the strong potential for practical applications such as highdensity storage devices.
