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Zero-Field Hedgehog Skyrmion Bubbles at Room Temperature in Ultrathin Heterostructures with Interfacial Dzyaloshinskii-Moriya Interactions - Javier Pulecio


With potential spintronic applications in memories, logic and sensors, isolating magnetic skyrmions as a ground state is of great interest. Moreover, determining the topology of the observed spin textures in films with strong Dzyaloshinskii-Moriya (DM) interactions and understanding the related topological effects on stability, size, and pinning is of critical importance. Using SQUID magnetometry, Lorentz TEM, scanning probe microscopy, and simulations, we probe multilayers of [ Pt \ Co \ Ir ]×N where the DM interactions originate from interfacial symmetry breaking in ultrathin films. We tune the intrinsic properties of these films to reduce the critical DM interaction necessary to nucleate hedgehog skyrmion bubbles at room temperature as an energetically favorable in zero-field. I will demonstrate their stability and propensity for pinning by isolating circular skyrmion bubbles in continuous films with structural disorder and inflate them to various sizes [2]. Interestingly, I will show a critical size above which hedgehog skyrmions bubbles lose circular symmetry, taking up an irregular shape much like a soap bubble. I will conclude by discussing our recent room temperature experiments of densely-packed skyrmion lattice clusters in zero-field, which prior to this, has been observed in single crystal materials under cryogenic temperature and applied fields.

[1] Pulecio, J. F., Hrabec, A., Zeissler, K., White, R. M., Zhu, Y., & Marrows, C. H. (2016). Hedgehog Skyrmion Bubbles in Ultrathin Films with Interfacial Dzyaloshinskii-Moriya Interactions, 12. Materials Science. ArXiv ID : 1611.06869

[2] Pulecio, J. F., Hrabec, A., Zeissler, K., Zhu, Y., & Marrows, C. H. (2016). Phase Transitions of Chiral Spin Textures via Dipolar Coupling in Multilayered Films with Interfacial DMI. ArXiv ID : 1611.00209