| We demonstrate that the chemisorption of a dodecanethiol (C12H 25SH) self-assembled monolayer on the surface of a Au film alters the coercivity Hc of an underlying Co film when exposed to a nearly perpendicular magnetic field. This is measured using the planar Hall effect. In particular, we observe time dependent shifts in the transverse resistance peaks, which appear at the coercive field of the Co film, for thiolated samples exposed to nearly perpendicular magnetic fields. We believe that shifts in Hc are due to a magnetostatic biasing effect originating at the Au-thiol interface which alters the Co domain structure during the magnetization reversal process. The time dependent shifts could be due to thiol island formation and evolution which is known to occur for incomplete SAM coverage. Micromagnetic simulations confirm the changes could be caused by the magnetized thiol islands. We have also observed statistically significant differences in the absolute percentage change between samples stored under vacuum and ambient conditions. This could prove surface preparation and history are important factors in determining the magnitude of the Au-thiol magnetic moment. |
