Domain wall motion induced magnetophoresis in unpatterned perpendicular magnetic anisotropy Co layers with Dzyaloshinskii-Moriya interactions

Magnetophoresis of micrometer sized superparamagnetic beads on sputtered Ir/Co(1.2 nm)/Ir multilayers with perpendicular magnetic anisotropy has been investigated. We show that domain walls motion in these layer systems is controlling the motion of the beads in an aqueous environment, where the domain wall motion is induced by varying perpendicular external magnetic fields of several kA/m. The magnetic fields of the Néel type walls, and forces calculated based on micromagnetic simulations of their structure, are consistent with viscous forces observed in the experiment. We show that the cylindrical domains can be used to efficiently gather originally scattered beads in a small area.