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

Abstract

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 ( $L$ ), as it is the case of Ho, induce an anisotropic interfacial exchange coupling.

Keywords: AFM exchange coupling; X‐ray magnetic circular dichroism spectroscopy; hybrid metal‐organic interfaces; magnetic anisotropy; rare‐earths.