No abstract

Recently, magnetic skyrmion has attracted much attention due to its potential application in racetrack memory and other nanodevices. In bulk chiral magnets with non-centrosymmetric crystal structures, skyrmion lattice phase has been extensively observed. However, in film or multilayers with interfacial Dzyaloshinskii–Moriya interaction, individual skyrmion is often observed. Here, we report a short-ordered skyrmion lattice observed in [Ta­(5.0 nm)/CoFeB­(1.5 nm)/MgO­(1.0 nm)]15 multilayer in a remnant state. The structure, stabilization, and reversal of these skyrmions are discussed. Applying a slightly tilted in-plane magnetic field caused reversal of the skyrmion lattice. This reversal came from disappearance of skyrmions and nucleation of new skyrmions in the interstitial regions of the lattice. Also, we investigated how the skyrmion lattice depended on the CoFeB thickness. Our findings provide a pathway to stabilize and reverse the skyrmions in multilayers films.

The stabilization of skyrmion bubbles in [Ta(tTa)/CoFeB(1.1 nm)/MgO(1.0 nm)]15/Ta(2.0 nm) magnetic multilayers with perpendicular magnetic anisotropy is investigated. The size of the skyrmion bubbles can be controlled by tuning the Ta interlayer thickness. Because the perpendicular anisotropy constant is large in samples with a thin Ta interlayer, we can observe nanoscale skyrmion bubbles in our system. This finding provides a means to control the skyrmion size without using an external magnetic field. Moreover, we found that skyrmion bubbles can be created by a magnetic tip and subsequently be deleted. Our novel findings provide insight into skyrmion-based spintronic devices.