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We report on advanced metal organic spin architectures constituted by metal (manganese, iron, copper) phthalocyanine molecules magnetically coupled with ferromagnetic layer(s) through a graphene (Gr) spacer. The highly corrugated moiré superstructure of Co-intercalated Gr/Ir(111) drives the assembly of evenly-spaced molecular bits, providing preferential adsorption regions for the phthalocyanine molecules. Our X-ray absorption and photoemission results show that the Gr layer shields the electronic/magnetic state of the molecules, screening the electronic interaction with the metallic surface while allowing for magnetic coupling, as proved by X-ray magnetic circular dichroism. Mn-, Fe- and Cu-phthalocyanines assemble on Gr/Co with identical structural configurations, but MnPc and FePc are strongly antiferromagnetically coupled with Co up to room temperature, while CuPc couples ferromagnetically with weaker thermal stability. The magnetic alignment is induced by a superexchange interaction, driven by the molecular orbitals responsible of the magnetic ground state and electronically decoupled from the underlying metal via the Gr layer, as confirmed by ab initio theoretical predictions. The tunable parameters to further optimize the system are the magnetic moment and anisotropy energy of both MPc molecules and intercalated Gr substrate, to reach room temperature remanence. We will show that, by exploring molecular building blocks with diverse metallic centers and different structure/magnetic state of the substrate, the best configuration can be identified. These archetypal spin interfaces can be prototypes to demonstrate how antiferromagnetic/ ferromagnetic coupling can be optimized by selecting the molecular orbital symmetry, paradigmatic examples to exploit in surface-supported molecular spin electronics.
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