The Role of Rare-Earth Atoms in the Anisotropy and Antiferromagnetic Exchange Coupling at a Hybrid Metal-Organic Interface

Magnetic anisotropy and magnetic exchange interactions are crucial parameters that characterize the hybrid metal-organic interface, a key component of an organic spintronic device. It is shown that the incorporation of 4f RE atoms to hybrid metal-organic interfaces of CuPc/REAu2 type (RE = Gd, Ho) constitutes a feasible approach toward on-demand magnetic properties and functionalities. The GdAu2 and HoAu2 substrates differ in their magnetic anisotropy behavior. Remarkably, the HoAu2 surface promotes the inherent out-of-plane anisotropy of CuPc, owing to the match between the anisotropy axis of substrate and molecule. Furthermore, the presence of RE atoms leads to a spontaneous antiferromagnetic exchange coupling at the interface, induced by the 3d-4f superexchange interaction between the unpaired 3d electron of CuPc and the 4f electrons of the RE atoms. It is shown that 4f RE atoms with unquenched quantum orbital momentum (L$L$), as it is the case of Ho, induce an anisotropic interfacial exchange coupling. The incorporation of 4f rare-earth atoms at hybrid metal-organic interfaces provides modulation of the magnetic properties related to spin-orbit effects. An interfacial antiferromagnetic exchange coupling is achieved, which shows strong anisotropy, depending on the quantum orbital state of the rare earth. This is a route toward advanced functionalities in molecular spintronics, integrating magnetic and optoelectronic properties. image