Voltage-tunable magnetic hysteresis and domain patterns by electrochemical reactions

• Applicant: Professorin Dr.-Ing. Karin Leistner
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 400178764

The control over magnetic properties in thin films plays a pivotal role in a multitude of modern device proposals in the fields of spintronics and magnet-based fluidic lab-on-chip systems. The manipulation of magnetism by an external voltage is strongly discussed as an energy-efficient alternative to current-based approaches that suffer from Joule heating. Within the research field of voltage control of magnetism, the electrochemical (magneto-ionic) control of nanoscale magnetism is a rapidly emerging topic. Both large effects and non-volatile setting of magnetic states by an external voltage come within reach when exploiting electrochemical phase transformations in magnetic films.In the proposed project we want to investigate reversible electrochemical reactions for voltage-tuning the magnetic hysteresis and domains of metal/oxide films. We intend to use Fe- and Co-based magnetic thin films as electrodes and liquid electrolytes that enable enhanced electric field effects and high ionic mobility at the magnet/electrolyte interface. The role of structural, compositional and microstructural variations occuring through electrochemical transformations will be analyzed and correlated with magnetic property changes. We expect to identify the key influencing factors and the conditions for enhanced reaction layer thickness and high reversibility of the magneto-ionic reactions. We will strive for a tunable Fe or Co layer with non-volatile behavior, where the magnetic state can be set by a moderate voltage and small initial current. The combination of such tunable top layers with bottom layers exhibiting perpendicular magnetic anisotropy promises to exponentiate the variability of magneto-ionic effects. Ideally, reversible magneto-ionic spin reorientation will be achieved within several nanometers.To track local magnetic changes during polarization within the electrolyte, an electrochemical cell compatible with Kerr microscopy will be developed. This in situ Kerr microscopy setup promises to resolve, for the first time, the local effect of magneto-ionic reactions on magnetic domains when using liquid electrolytes. Magneto-ionic effects in patterned structures will be investigated for voltage-tunable stray field landscapes and domain wall traps.

• DFG Programme: Research Grants