Control of the magnetic domain of Pt/Co/Ru/MgO multilayer: Effect of Co thickness and Ru insertion

In this study, we investigated the effect of Co film thickness and Ru insertion on the magnetic domain structure of a Pt/Co/Ru/MgO system during the magnetization reversal process. It was observed that with increasing Co thickness, the magnetization process systematically changed from the dendrite-like domain growth region to an isolated skyrmion bubble generation region through the suppression of domain wall motion and the decrease in the nucleation field. In addition, by Ru insertion, a similar systematic change in the magnetization reversal process was observed in a thinner Co film while maintaining the Co thickness dependent trend. It was also found during our study that the change in the magnetization reversal process could be inferred by observing the shape of the magnetization curve. Moreover, our experiment showed that once skyrmion bubbles were generated, the Ru inserted Pt/Co/MgO system was stable even after the removal of the magnetic field. This magnetic-field insensitivity of skyrmion bubbles is a pivotal characteristic and could be of great advantage for many spintronics applications.