THE SPINTERFACE PROBLEM: AB-INITIO STUDIES OF FE-PHTHLOCYANINE ON TRANTITION-METAL OXIDES.

At the interface between a transition-metal oxide and a metal-organic molecule, electrons form interesting hybrid electronic states that characterize what is commonly called an organic spinterface. The central idea of our study is the possibility of exciting a spin coherent wave inside the substrate through a light-induced excitation of the molecule - in other words, actively perturbing the spinterface to modify its magnetic state. In this framework, the spinterface is studied for its electronic, magnetic and optical properties through ab-initio approaches. Specifically, we selected the transition-metal oxides: NiO(001), CoO(001) and Cr2O3(0001) as substrates. These materials are antiferromagnetic at high and/or room temperature and are characterized by low spin-orbit interaction, making them promising candidates for spin-excitation transport. For the metal-organic molecule, we chose Fe-phthalocyanine, a versatile species valued for its adaptability across various applications. In addition to the insights specific to each molecule/substrate combination revealed by our ab-initio simulations, three main findings emerged regarding the goal of activating the spinterface by light. First, significant hybridization between the molecule and the substrate is advantageous for maximizing the transfer of the light-induced molecular excitation onto the magnetic couplings between substrate spins. Second, to impact the substrate's magnetic couplings, this hybridization needs to be spin-unbalanced. In this regard an adsorption configuration breaking the spin symmetry of the substrate is sufficient, so that the adsorption of a magnetic molecule is not required. Third, effective control over spinterface tunability requires a distinct retention of molecular and substrate character: hybridization should not be so strong that they become indistinguishable. In terms of light excitation spectra, this translates into high-intensity transitions between states with identifiable molecular and substrate characteristic.