Metastable multi-domain state in ultrathin films with Dzyaloshinskii-Moriya Interaction

Helical spin structures such as skyrmions and chiral domain walls are stabilized in magnetic films with strong Dzyaloshinskii Moriya interaction (DMI) [1,2]. The chiral spin state is the ground state when the ratio of the effective DMI field to anisotropy field is greater than 2/pi [3]. However, even when the DMI is too weak to generate a chiral ground state, such states can be metastable if the uniform state is appropriately perturbed [1,4].Here, we show that an in-plane applied field reduces the energy barrier for domain wall formation, and provides a simple technique to generate a multidomain state in uniform magnetic films. Further, we identify that the threshold between the stable single-domain state and the metastable multidomain state can be controlled by two parameters-demagnetizing energy and geometrical confinement. We use these parameters to create isolated geometrically confined magnetic bubbles in patterned discs of Pt/Co/GdOx multilayers. These bubbles may provide insight into the mechanism of creation of skyrmions in magnetic thin films with strong DMI.\\[4pt] [1] A. Fert et al., Nat. Nanotech., 8, 152-156 (2013);\\[0pt] [2] S. Emori et al., Nature Materials 12,61-616 (2013);\\[0pt] [3] S. Emori, et al., arXiv:1308.1432v2(2013);\\[0pt] [4] N. Perez, et al., Appl. Phys. Lett.104, 092403(2014)