Imaging room-temperature skyrmions and magnetic domains patterns at zero magnetic field in symmetric Pt/Co/Pt heterostructures

Full text: Magnetic skyrmions are small-sized swirling spins textures that have been widely studied due to their interesting physical properties and potential advantages for novel magnetic memory technologies. Their stability, topological structure and motion by ultra-low current are suitable for such spintronic devices. Nevertheless, their features must be highly controlled in order to acquire stability and reproducibility on the nucleation and motion processes. A major step toward this goal lies on the room-temperature nucleation and stabilization of skyrmions without the need for any external force. In this work, we investigated the formation of zero field skyrmions at room temperature in symmetric Pt/Co/Pt multilayers. Magnetic multilayers SiO2//[Pt (1 nm)/Co (t)/Pt (1 nm)] x 15 (t = 0.5, 0.8, 1.0 and 1.5 nm) were fabricated by magnetron sputtering. The magnetic domains patterns were imaged by magnetic force microscopy (MFM) in the as grown state, at room temperature and zero magnetic field. By carefully controlling the physical properties across the ferromagnetic heavy metal interface (FM/HM), zero field labyrinthine domains observed for thicker Co layers evolve to isolated skyrmions for thinner Co layers. Scanning transmission X-ray microscopy (STXM) was also carried out to confront shape and size of isolated magnetic skyrmions. For the labyrinthine state both periodicity and domain wall width increase as the Co thickness decreases from 1.5 nm to 0.8 nm. Further studies performed by micromagnetic simulations indicate that the interfacial Dzyaloshinskii-Moriya interaction also plays a major role for the stabilization of room-temperature zero field skyrmions. These findings open new perspectives to use zero field skyrmions in skyrmionics devices. (author)