Chemical tuning of magnons in NiO(001) by Fe-phthalocyanine adsorption

Magnonics is a rapidly growing field that is nowadays broadly recognized as a paradigm shift for information and communication technologies. In this context, antiferromagnetic materials are particularly relevant due to the lack of stray fields and their faster dynamics, with frequencies in the THz range and longer spin relaxation times. Herein, we investigate the chemical tuning of magnons in a prototypical antiferromagnetic transition metal oxide through the creation of a hybrid heterostructure formed by an Fe-phthalocyanine layer over a NiO(001) substrate. Our first-principles calculations for the hybrid material allow us to evaluate the effect of the adsorbed molecules on the electronic structure, charge transfer and magnetic exchange couplings of NiO. In particular, we observe an electron density flow from the O towards the Ni atoms in the substrate, and from the O atoms towards the molecule at the interface. As a result, the magnetic couplings are enhanced by 7.7% at the surface, accompanied by a decrease by 19.1% in the layer below the surface. Interestingly, our results predict a shift of the magnon frequencies by ∼10 meV in the optical branch. This work provides a new step towards the design of molecular controlled magnetic materials for magnonic applications.