Field angle-dependent bubble lattice formation in Re/Co/Pt multilayers

Formation of bubble lattices stable at room temperature is investigated in asymmetric epitaxial [Re(1 nm)/Co(d
Co
)/Pt(1 nm)]
20
multilayers with thickness of the Co component layer, d
Co
, ranging between 0.8 nm and 2.0 nm. This thickness range covers uniaxial anisotropy transition from perpendicular to in-plane with d
Co
increase. We study evolution of domain structure at remanence depending on the sample magnetic history described by: (i) applied field inclination angle measured from the sample plane and (ii) the field strength. The bubble lattice appears only in a narrow field inclination angle range, being specific for d
Co
. With increase in d
Co
the required inducing field rotates from parallel to perpendicular orientation relative to the sample plane. The maximum density of the bubble lattice decreases from 18 μm
^-2
to 1 μm
^-2
with d
Co
increase from 0.8 nm to 2.0 nm. Interpretation of the experimental results is supported by density-functional theory calculations and micromagnetic modelling. Obtained experimental and theoretical results suggest that the observed bubbles are topologically protected skyrmions.