Control of magneto-optical properties of cobalt-layers by adsorption of α-helical polyalanine self-assembled monolayers

The adsorption of chiral molecules was recently shown to trigger a change in the magnetisation of mesoscopic magnetic domains in a ferromagnetic underlayer. In this work, we investigated the macroscopic (magneto-)optical response of chemisorbed α-helical polyalanine self-assembled monolayers (SAMs) on a gold and gold-capped-cobalt thin film on Au substrates using spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy and microscopy. The optical and magneto-optical spectra reveal selective chemisorption of the α-helical polyalanine molecules depending on the orientation of the substrate remanent magnetisation during the SAMs process. Moreover, a sign change of the magneto-optical response was observed in some of the magnetic substrates after the chiral SAMs formation. Adsorption of α-helical polyaniline self-assembled monolayers onto magnetic substrates containing a thin Co layer determines the magneto-optical response.