Affiliation:
1. Electrochemical Sensors and Energy Storage Institute of Chemistry Chemnitz University of Technology 09107 Chemnitz Germany
2. Magnetic Functional Materials, Institute of Physics Chemnitz University of Technology 09107 Chemnitz Germany
3. Center for Materials Architectures and Integration of Nanomembranes (MAIN) Chemnitz University of Technology 09107 Chemnitz Germany
4. Institute of Ion Beam Physics and Materials Research Helmholtz‐Zentrum Dresden‐Rossendorf 01328 Dresden Germany
Abstract
AbstractMagneto‐ionics, as the electrochemical reconfiguration of magnetic materials at low gating voltages, is a highly energy‐efficient alternative to control magnetism. For the fastest magneto‐ionic concept based on hydrogen, fundamental mechanisms are currently under debate, mainly because quantitative compositional information inside the magnetic materials upon gating is lacking. Using the electrochemical hydrogen loading of Co/Pd multilayers with perpendicular anisotropy, this study demonstrates that the hydrogen concentration inside the magnetic material determines its magnetic properties. Hydrogen concentrations up to a maximum of (0.24 ± 0.01) hydrogen atoms per metal atom can be set deterministically by voltage and are quantified via flow‐cell coulometry. With increasing hydrogen concentration, a continuous increase in coercivity of up to 15% and a decrease in magnetic domain‐wall velocity by an order of magnitude are observed using in situ MOKE microscopy. This enables the voltage‐controlled stop‐and‐go of domain walls. These magneto‐ionic effects can be explained by an increasing perpendicular anisotropy with increasing hydrogen content in Co/Pd multilayers, which is supported by theory. Importantly, the approach should be transferable to other ionic systems, such as lithium‐ or oxygen‐based ones, where it can uncover the yet hidden effects of ionic concentration on the magnetic properties and guide the design of functional magneto‐ionic devices.
Funder
Deutsche Forschungsgemeinschaft
European Research Council