PhD Thesis Defense- Iker Gallardo

CFM Seminars

Iker Gallardo
CFM First Flor Seminar Room
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PhD Thesis Defense- Iker Gallardo **Title: Magnetic properties of Co on different environments** **Supervisors: **Andres Arnau and Fernando Delgado **Research group: **Modelisation and Simulation group ** ** **When:** November 4, 2019 (11:00h) **Where:** CFM SEMINAR ROOM [ **Download pdf**]( ### **Summary** We combine density functional theory (DFT) calculations and a multiorbital many-body Hamiltonian approach to shed light on magnetic properties of Co adsorbed on h-BN depending on the adsorption site. These methods reveal an out-of-plane easy axis anisotropy for atop N site and hard axis for hollow site, with an electronic configuration close to 3d8, corresponding to a spin S = 1. Then, we compare our results with x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD) and x-ray magnetic linear dichroism (XMLD) measurements on Co/h-BN/Ir(111) and Co/h-BN/Ru(0001). XAS and XMCD data show large (14 meV) out-of-plane anisotropy for Co/h-BN/Ru(0001) and almost isotropic for Co/h-BN/Ir(111), while both have an electronic structure compatible with spin S = 1. We use this information to determine the atop N adsorption of Co on h- BN/Ru(0001) and hollow for the Co on h-BN/Ir(111). XMLD data together with DFT and multiorbital Hubbard model results suggest that the different adsorption sites induce dissimilar anisotropy of Co. Finally, we explain from DFT calculations the counterintuitive downward shift of the Au(111) surface state measured by angle resolved photo-emission spectroscopy (ARPES) when two homothetic Co-coordinated metal-organic nanoporous networks (MONN) are self-assembled. We associate this effect to the weak Co-substrate hybridization and show that it appears with different adatoms and substrates. ![]( Top views of the 4 4 supercell for h-BN on Ir(111) surface, after relaxation of the h-BN monolayer in the Z direction. Green and blue spheres represent B and N atoms, respectively, while light blue are the top most layer Ir(111) surface atoms.