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After more than 15 years of intense exploration, graphene, a prototypical bidimensional material, has not exhausted its interest. One example is given by the coupling of graphene with ferromagnetic systems, that can open new perspectives in the engineering of spintronic devices, high-density magnetic storage, and permanent magnets. Surprisingly, graphene - iron (Fe) interfaces have been little explored, despite iron being the most widespread transition metal, not expensive and, most importantly, with a strong magnetic response.
Aware of the fundamental and technological relevance of the field, a team of scientists, part of a long-standing collaboration between groups in CNR Nano, Modena, and La Sapienza, Roma, investigated the topic and recently published the results in Physical Review Materials. The theoretical calculations (using the MaX flagship code QuantumESPRESSO) were performed by the team composed of C. Cardoso, D. L. Valido, A. Ferretti, and D. Varsano from CNR Nano, while M.G. Betti’s group at La Sapienza conducted the experimental work.
The growth of Fe-graphene interfaces is very challenging: the team used as a starting point graphene grown on iridium (Ir) and then intercalated a layer of Fe under graphene, preventing the formation of Fe-C and the Fe-Ir intermixing. The resulting interface is made of an artificial two dimensional Fe layer in registry with the Iridium surface and capped by graphene. Combining experiments and simulations, the researchers gained a detailed insight into the physical properties of this unexplored graphene-Fe interface. They have shown that the graphene top layer, besides allowing for the growth of the interface, has the role of a protective membrane for Fe preventing its oxidation and moreover promoting the transition of Fe to strong ferromagnet. This study sheds light on the powerful playground that this new interface can offer for designing new magnetic/spintronic devices.
Top: side view of the Gr/Fe/Ir(111) structure showing the graphene corrugation and charge difference isosurfaces; bottom: Band structure and projected density of states (pDOS) computed within DFT for Gr/Ir(111) and Gr/1 ML Fe/Ir(111).
Magnetic response and electronic states of well defined Graphene/Fe/Ir(111) heterostructure. Claudia Cardoso, Giulia Avvisati, Pierluigi Gargiani, Marco Sbroscia, Madan S. Jagadeesh, Carlo Mariani, Dario A. Leon, Daniele Varsano, Andrea Ferretti, and Maria Grazia Betti. Phys. Rev. Materials 5, 014405