Speaker
Description
The term magneto-ionics has been coined for electrochemical reactions, which are utilised for the modification of magnetic properties. In this rapidly growing field, one key goal is to enable a complete and reversible On- and Off-switching of magnetism. Here, we achieved this goal via hydrogen-charging of nanoporous (np) Pd(Co) prepared via electrochemical dealloying.
Owed to their high surface-to-volume ratio, nanoporous metals are particularly promising for ionic applications, as it becomes possible to change bulk properties, like magnetization, via surface reactions. As ionic transport is promoted in the nanoporous structure, this class of materials also allows a fast intercalation of ions in the porous host structures.
An in situ electrochemical cell in a SQUID magnetometer was used to track the change of magnetic properties directly as a function of electrochemical bias. Hydrogen intercalation is shown to increase the magnetic moment by up to 600%. Extensive magnetic and structural characterization revealed that nanometre-sized clusters rich in Co are buried under the nanoporous structure, as a natural side product of the dealloying synthesis route. These clusters, responsible for superparamagnetic properties of the original material, are magnetically coupled by interstitial hydrogen atoms, causing the unexpectedly large switching effect.
By in situ dilatometry and in situ resistometry we show that not only magnetic properties of npPd(Co) can be altered by hydrogen-charging, but also length and resistance can be reversibly adjusted. Hydrogen-tuneable magnetism, resistance, and length have great potential for the design of novel hydrogen sensors based on nanoporous Pd(Co).
Financial support by the Austrian Science Fund FWF (P30070-N36) is acknowledged. This work was performed in the framework of the inter-university cooperation of TU Graz and Uni Graz on natural sciences (NAWI Graz).
| Speaker Country | Austria |
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