Room-temperature magnetic field stability of skyrmion bubbles in ultrathin films with Dzyaloshinskii-Moriya interaction

The Dzyaloshinskii-Moriya interaction (DMI) at heavy-metal/ferromagnet interfaces can stabilize chiral spin textures, such as magnetic skyrmions. Magnetic skyrmions are topologically protected spin textures that exhibit fascinating physical behaviors and have potential in highly energy efficient spintronic device applications. However, the room temperature stability of skyrmion bubbles has not been quantified experimentally. Here, we show that when the ratio of the DMI effective field to the perpendicular anisotropy field is large (domain wall energy is low), expanding bubble domains leave behind fine-scale magnetic dendritic structures. These dendritic structures can be manipulated to form stable skyrmion bubbles, consisting of chiral Néel domain walls. To quantify the stability of the skyrmion bubbles, we imaged skyrmion bubbles in Pt/Co/GdO_x films using wide-field Kerr microscopy as a function of in-plane and out-of-plane field. Histograms of the skyrmion annihilation fields were obtained for several in-plane fields. We show that in-plane fields reduce the annihilation threshold of the skyrmions, lowering the barrier to annihilation. The skyrmion annihilation field becomes deterministic at large in-plane fields above the DMI effective field. Micromagnetic simulations qualitatively confirm these measurements and suggest an enhanced skyrmion stability due to the DMI.