Magnetic structure of the inverse opal-like structures: Small angle neutron diffraction and micromagnetic simulations

•Magnetic structure of Co inverse opal was studied by SANS and micromagnetic modelling.•The diffraction patterns and field-dependencies of magnetic scattering were analyzed.•3 types of the interplay between the magnetic field and the ice rule were considered.•Results agree with the spin-ice model predictions although vortex states were found.