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Topologically protected magnetic features including Skyrmions have drawn a great deal of attention recently for future computing applications due to the unprecedented efficiency with which they can be manipulated by spin current. These features are stabilized by the Dzyaloshinskii-Moriya Interaction (DMI), which favors a chiral winding of neighboring electron spins. In this talk, we examine the impact of an interface-induced DMI on the structure of magnetic domain walls (DWs) in asymmetric [Pt/Co/Ni/Ir]xN based superlattices where structural inversion symmetry is broken. The interfacial DMI vector is measured by examining the asymmetric growth of magnetic bubble domains via Kerr microscopy where both in-plane and perpendicular magnetic fields are applied. Experimental growth velocity measurements are fit to the dispersive stiffness model[1] based on highly anisotropic energy of Dzyaloshinskii DWs coupled with an attempt frequency that depends on the DW’s internal magnetization akin to chiral damping.[2] DWs were directly imaged using high resolution Lorentz mode transmission electron microscopy on thicker asymmetric superlattices which display a remnant labyrinth domain pattern characteristic of bubble materials. Striking features of reconstructed Lorentz induction maps associated with Dzyaloshinskii DWs are presented and discussed theoretically. We confirm a preferred chirality of Néel domain walls in our system and demonstrate the ability to tune the DMI constant through variations in thickness and composition.
[1] J. P. Pellegren, D. Lau, and V. M. Sokalski, "Dispersive Stiffness of Dzyaloshinskii Domain Walls," Physical Review Letters vol. 119, p. 027203, 2017.
[2] E. Jue, C. K. Safeer, M. Drouard, A. Lopez, P. Balint, L. Buda-Prejbeanu, et al., "Chiral damping of magnetic domain walls," Nat Mater, vol. 15, pp. 272-277. 2016.
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