Schematic representation of the different stages of our magnetar formation scenario. The dashed line encloses the region of the fallback (orange arrows). Red and white lines represent the magnetic field lines and fluid motions, respectively. Ω and E_ϕ stand for the angular rotation frequency and the azimuthal component of the electromotive force, respectively. B_ϕ and B_r are the axisymmetric azimuthal and radial magnetic fields, and δB_⊥ is the non-axisymmetric perpendicular magnetic field.