Morphological stripe-bubble transition in remanent magnetic domain patterns of Co/Pt multilayer films and its dependence on Co thickness

We report a phase transition in the topology of the magnetic domain pattern exhibited by ferromagnetic Co/Pt multilayer films at remanence. We found that the remanent magnetic domain pattern topology and density strongly depend on the magnetic history, in particular on the magnitude of the previously applied field. The magnetic pattern, which generally forms a maze of stripe domains, transforms into a bubble pattern and the domain density drastically increases when the magnitude of the previously applied field approaches a specific value, typically 70-90% of the saturation field value. We mapped out this topological phase transition as a function of the previously applied field magnitude as well as Co thickness. This led to the estimate of most favorable conditions to maximize magnetic domain density.