Magneto-Ionic Switching of Superparamagnetism

Markus Gößler, Heinz Krenn, Roland Würschum

Research output: Contribution to conferenceAbstract


Nanoporous materials are promising candidates for the voltage-control of magnetism in electrochemical setups due to their large surface-to-volume ratios. Here, we introduce the class of dealloyed nanoporous metals in the field of magneto-ionics. Electrochemical dealloying is a selective corrosion process from an alloy, which allows preparing a great variety of metallic nanoporous structures. While the lesser noble element is gradually removed, the nobler component rearranges during the corrosion process forming nanometre-size ligaments. Inevitably a small fraction of the sacrificial element is buried in ‘clusters’ under the noble metal surface during dealloying [1], which we utilised for the magnetic functionalisation of our structures. A ferromagnetic sacrificial element in the dealloying process, gives the option to prepare nanoporous structures with embedded magnetic nanoparticles in a one-step process.
In this work nanoporous palladium containing clusters of cobalt -npPd(Co)- is prepared from a CoPd alloy. High-resolution TEM in combination with elemental mapping techniques revealed a residual cobalt concentration of about 8 at% agglomerated in clusters with an average size of 1.5-2 nm. Palladium is not only a high-susceptibility paramagnet attractive for magnetic tuning, but also known for its ability to store large amounts of hydrogen in the crystal lattice. Our magneto-ionic approach attempts to bias magnetic properties of Co-clusters in the Pd-matrix via electrochemical hydrogenation.
Hydrogenation was conducted in an in situ electrochemical cell in a SQUID-magnetometer, allowing a direct determination of the changes in magnetisation. Upon voltammetric cycling in the electrochemical hydrogen regime magnetisation was reversibly altered by more than 600%, corresponding to a complete On- and Off-switching of magnetism. A novel magneto-ionic mechanism, based on a RKKY-mediated cluster coupling upon hydrogenation, is proposed to account for the unexpectedly large changes upon hydrogenation [2].
This work is financially supported by the Austrian Science Fund (FWF): P30070-N36.
[1] T.Krekeler, A. V. Straßer, M. Graf, K. Wang, C.Hartig, M. Ritter, J. Weissmüller, Mater. Res. Lett. 5, 314, (2017)
[2] M.Gößler, M. Albu, G. Klinser, E.-M. Steyskal, H. Krenn, R. Würschum,
Small 15, 1904523, (2019)


SeminarEnergy Efficient Magnetoelectric Materials by Ionic Approaches: Fundamentals, Challenges and Perspectives
CityBad Honnef
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  • Advanced Materials Science


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