Revealing the morphology and the magnetic properties of single buried cobalt-ZnTPP hybrid interfaces by ferromagnetic nuclear resonance spectroscopy

Abstract

The deeply buried, yet most important part of any spintronic device is the interface. This is even more interesting and much more complex when soft, light materials like organic molecules are in contact with an inorganic metallic electrode. Hence, exceptional care is required to better understand the phenomena driven by this type of organic/inorganic interfaces. To this end, ferromagnetic nuclear resonance (FNR) spectroscopy studies were performed to investigate the morphology and the magnetic properties of the hybrid organic-inorganic interfaces when zinc tetraphenyl porphyrin (ZnTPP) molecules are at the vicinity of ferromagnetic metallic cobalt (Co) layers. The FNR experimental results show that when ZnTPP is deposited on top of Co the resulting interface is smoother and sharper compared to the more extended interface obtained when Co is deposited on top of ZnTPP. The shape of the spectra suggests that no chemical bonds take place between the interfacial Co atoms and the ZnTPP molecules and that interactions at the interfaces are governed by weak van der Waals forces. Finally, FNR also showed that the magnetic anisotropy at the Co-ZnTPP hybrid interfaces is reduced compared to the magnetic anisotropy of the Co atoms inside the Co films.