Influence of Pt spacer thickness on the domain nucleation in ultrathin Co/Pt/Co trilayers

The effect of varying the interlayer coupling between two 0.6 nm thick Co layers with perpendicular anisotropy on their magnetic ground state and the domain nucleation processes during a field reversal was studied. A transition from out-of-plane to in-plane anisotropy was revealed as the Pt spacer thickness decreased below 1.6 nm. For Pt thicknesses in the range of 1.6–5.4 nm, domain nucleation occurred in both Co layers in a correlated manner, and subsequent motion of the domain walls proceeded as though bound together. A transition to uncorrelated domain nucleation and independent wall motion was observed at Pt thicknesses above 5.4 nm. Both conventional and “asymmetrical” domain nucleation centers were observed in the whole range of platinum spacer thicknesses.