Magnetic domain propagation in Pt/Co/Pt micro wires with engineered coercivity gradients along and across the wire

Pt(15 nm)/[Co(0.6 nm)/Pt(1.5 nm)]4 multilayers with perpendicular magnetic anisotropy were patterned into several-micrometer wide wires by electron-beam lithography. Bombarding the wires with He+ ions with a fluence gradient along the wire results in a spatial gradient of switching fields that allows a controllable positioning of domain walls. The influence of the reduced anisotropy near the wire edges causes a remanent state in which the reversal close to the long edges precedes that in the middle of the wires. Experiments using Kerr microscopy prove this effect and micromagnetic simulations corroborate that a decrease of the anisotropy at the edges is responsible for the effect.