Controlling interfacial Dzyaloshinskii-Moriya interaction and magnetic skyrmions in Ru/Pd/Co/Ni based heterostructure

Dzyaloshinskii-Moriya interaction (DMI) leads to the formation of non-trivial spin textures such as magnetic skyrmions which are being investigated heavily to be incorporated in future nanomagnetic memory and computing devices. Thus, efficient ways of controlling DMI are needed to stabilize and manipulate skyrmions in practical devices. DMI at heavy metal/ferromagnet interface vary widely in size and sign, presenting a possibility to fabricate multilayer systems with precise DMI values by designing different interfaces. Here we report controlling DMI in multilayer heterostructures of (Co/Ni)_n/Pd(t)/Ru with varying Pd layer thicknesses (t). We employed magneto-optic Kerr effect (MOKE) imaging to capture asymmetric bubble domain expansion under different in-plane magnetic fields and estimated DMI in these samples. As DMI of opposite signs are produced by Co/Pd [1] and Co/Ru [2], the DMI was found to be tunable, e.g., from clearly Pd-like (i.e. left-handed) to essentially zero with a small reduction of Pd thickness. Furthermore, skyrmions are observed in these samples, whose size and density are explored under different interface characteristics. These results demonstrate a new interface design to regulate DMI and consequently skyrmions.

References:

[1] K. S. Ryu et al., Nat. Commun. 5, 3910 (2014)

[2] H. Yang et al., Nat. Mater. 17, 605 (2018)