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A novel Rutherford backscattering spectrometry (RBS) method is presented to investigate the interface between a solid surface and a surrounding liquid. The introduced measurement system allows to observe and quantify adsorption at the solid–liquid interface and the formation of the electrochemical double layer (EDL). BaCl2 as a bicomponent electrolyte and a Si3N4 membrane surface are chosen as a model system to prove the capabilities of the setup. The results of these RBS measurements are combined with electrochemical impedance spectroscopy (EIS) to validate the findings for the solid–liquid interface under study. Complementary results and discrepancies regarding the formation of the EDL are discussed. Author keywords: electrochemical double layer, electrochemical impedance spectroscopy, Rutherford backscattering spectroscopy, silicon nitride

High energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redox���based (magneto���ionic) voltage control of magnetism is a promising room���temperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magneto���ionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltage���induced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial in���plane anisotropy. In the initial iron oxide/iron films, N��el wall interactions stabilize a blocked state with high coercivity. During the voltage���triggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magneto���ionic deblocking mechanism, which relies on changes of the N��el wall interactions, and of the microstructural domain���wall���pinning sites. With this approach, voltage���controlled 180�� magnetization switching with high energy���efficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defect���controlled materials in general.

We report on a new versatile experimental setup for in situ Rutherford backscattering spectrometry at solid-liquid interfaces which enables investigations of electric double layers directly and in a quantitative manner. A liquid cell with a three-electrode arrangement is mounted in front of the beam line, and a thin Si3N4 window (thickness down to 150 nm) separates the vacuum of the detector chamber from the electrolyte in the cell. By minimizing the contribution of the window to the measurement, a large variety of elements at the solid-liquid interface with sensitivities far below one monolayer can be monitored. The attachment of Ba onto the Si3N4 surface as a function of contact time and pH value of the electrolyte solution was chosen as an example system. From our measurement, we can not only follow the evolution of the double layer but also derive limits for the point of zero charge for the Si3N4 surface. Our findings of 5.7≤pHPZC≤6.2 are in good agreement with values found in the literature obtained by other techniques. Despite focusing on a specific system in this work, the presented setup allows for a large variety of in situ investigations at solid-liquid interfaces such as, but not limited to, tracing electrochemical reactions and monitoring segregation, adsorption, and dissolution and corrosion processes.