Probing the electrochemical interface with in situ magnetic characterizations: A case study of Co/Au(111) layers

In this paper, we exploit the high sensitivity of the magnetism of ultrathin Co/Au(111) layer to study the electrochemical interface structure. Using in situ real time magnetic measurements (polar magneto-optical Kerr effect, PMOKE) it is established that the surface chemistry determines the surface magnetization anisotropy energy KSSurf and thereby the direction of magnetization at a given thickness. We next demonstrate that the magnetic properties are strongly modified by the hydrogen evolution reaction (HER) at CO-covered layers and exploit the data to study the reaction mechanism. We also take advantage of the sensitivity of KSSurf to the electric field to discuss the structure of the electrochemical interface at H- and CO-covered cobalt surfaces.