  Pairing of $\pi$ electronic state structures with functional or metallic
atoms makes them possible to engineer physical and chemical properties. Herein,
we predict the reorientation of magnetization of Co on hexagonal BN (h-BN) and
graphene multilayers. The driving mechanism is the formation of the tetrahedral
bonding between sp$^3$ and d orbitals at the interface. More specifically, the
intrinsic $\pi$-bonding of h-BN and graphene is transformed to sp$^3$ as a
result of strong hybridization with metallic $d_{z^2}$ orbital. The different
features of these two tetrahedral bondings, sp$^2$ and sp$^3$, are well
manifested in charge density and density of states in the vicinity of the
interface, along with associated band structure near the $\bar{K}$ valley. Our
findings provide a novel approach to tailoring magnetism by means of degree of
the interlayer hybrid bonds in 2D layered materials.
