Enhancement of magnetic domain topologies in Co/Pt thin films by fine tuning the magnetic field path throughout the hysteresis loop

• Morphology of magnetic domains in Co/Pt thin films changes with magnetic history.
• Domain morphology evolves from a maze to a bubble pattern when field approaches Hp.
• Domain morphology at remanence depends on magnitude Hm of previously applied field.
• A topological maze-to-bubble phase transition occurs at remanence when Hm is near H⁎.
• Density of oppositely aligned domains peaks up when Hm is near H⁎.

We have studied the influence of magnetic history on the topology of perpendicular magnetic domains in a thin ferromagnetic film made of [Co(8 Å)/Pt(7 Å)]50 multilayers. More specifically, we have followed the morphological changes in the domain pattern when applying a magnetic field perpendicular to the layer, throughout minor and major magnetization loops, and in the resulting remanent state. We carried out this study by using MFM microscopy with an in-situ magnetic field. We find that the morphology of the magnetic domain pattern is greatly influenced by the magnetic history of the material and that some features, such as the degree of bubbliness (i.e., the extent of bubble domain formation) and density of isolated domains can be enhanced by fine tuning the magnetic field path within the major hysteresis loop towards different remanent states. In particular, we see how hysteresis is correlated to irreversible changes in the domain morphology. More interestingly, we find that the magnetic domain morphology at remanence can be changed from an interconnected labyrinthine stripe state to a state of many separated bubble domains by fine tuning the magnitude of the field previously applied to the material. These results agree well with other findings, such as the magnetic reversal behavior and magnetic memory effects in Co/Pt multilayers, and provide opportunities for potential technological applications.