Local physical properties of magnetic molecules

Abstract

Advanced atomic force microscopy based techniques were developed to investigate local properties of individual well-separated adsorbed molecules, which can be applied to all kinds of supporting substrates independent of their conductivity. First, we find that due to the Smoluchowski effect a localized electrostatic dipole moment is present at the end of metallic tips. Since its positive pole points towards the surface, we are able to identify the chemical species in atomically resolved images on polar surfaces. We employed such tips to determine the exact adsorption geometry of single molecules on ionic bulk insulators. Moreover, we were able to detect magnitude and direction of the electrostatic dipole moment of adsorbed molecules. Secondly, if the tip is magnetic, we are even able to probe the short-range electron-mediated magnetic exchange interaction between the foremost tip apex atom and the sample atom directly below and thus established magnetic exchange force microscopy as a novel method to study magnetic sample systems with atomic resolution. By applying this new kind of magnetically sensitive force microscopy to a paramagnetic organo-metallic complex adsorbed on an antiferromagnetic bulk insulator, we find indications for a superexchange-mediated coupling between molecule and substrate.