Dependence of domain wall structures on repetition n in [Pt(0.5 nm)/Co(0.4 nm)]_n /NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]_n multilayers

The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers. In the antiferromagnetic coupled [Pt(0.5 nm)/Co(0.4 nm)]_n /NiO(1.1 nm)/[Co(0.4 nm)/Pt(0.5 nm)]_n multilayers with perpendicular anisotropy, the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers. In demagnetized states, relatively shifted domain walls in the two Co/Pt multilayers are observed, with net ferromagnetic stripes formed between them for the repetition number n less than 5, and the stripe width decreases with the increase of n. The occurrence of these features can be attributed to the competition between the interlayer coupling and magnetostatic energies.