First-principles exploration of sp-electron digital magnetic heterostructures: The case for CaO δ-doped with 2p-block elements boron, carbon, and nitrogen

•Ferromagnetic coupling is the favorable for both interlayer and intralayer spin interaction.•B-embedded DMH transforms from magnetic metal to magnetic semiconductor by considering Coulomb effect.•N-embedded DMH transforms from half metal to magnetic semiconductor by considering Coulomb effect.•Enhancing electronic correlation could not remove the degeneration of p states within the plane of δ-layer for C-embedded DMH.