Hydrogen Magneto-Ionics

Magneto-Ionics is all about controlling magnetism using electrochemical reactions (learn more about it here). Typically, electrochemical reactions are limited to the electrode surfaces, which makes large modifications of magnetic bulk properties a difficult task. As an example, think of thin layers of rust forming on iron when exposed to water and air, which would barely change the magnetism of a large piece of iron. In order to achieve large magneto-ionic effects, sample geometries with large surface-to-volume ratios, such as thin films or nanostructured materials, have been the focus of latest research (we also prepare them in our group, see here). Intercalation reactions, on the other hand, allow the movement of ions/atoms directly into the magnetic material, which maximizes the interaction volume and thus the impact on the magnetism of the material.

Such materials include battery electrodes, which can host large concentrations of lithium ions, or metals such as nickel and palladium, which can take up atomic hydrogen. In our lab, we explore such hydrogen- and lithium-intercalating materials for new magneto-ionic applications. The image below shows an example for a magneto-ionic effect based on hydrogen-intercalation. 

We currently study the effect of hydrogen-loading into a layered magnetic structure based on Pd/Co (left), which is kindly provided by the Hellwig group. Palladium can not only intercalate vast amounts of hydrogen into its crystal lattice, but also couples adjacent Co layers magnetically, which is exploited in the present magneto-ionic device. In her research project, Madeleine has demonstrated a coercivity increase upon hydrogen-loading of about 20%, which was reversible over several loading/unloading cycles (middle). For a better understanding, the corresponding magnetic hysteresis loops upon hydrogen-loading and -unloading are schematically drawn on the right.

Contact:

Dr. Markus Gößler

tel.:       +49 (0) 371 531 37533
e-mail:  markus.goessler@…
room:   1/150

Further reading:

• M. Gößler, S. Topolovec, H.Krenn, R. Würschum, Nanoporous Pd_1-xCo_x for hydrogen-intercalation magneto-ionics,
  APL Mater. 9,041101 (2021), https://doi.org/10.1063/5.0039136
• M. Gößler, M. Albu, G. Klinser, E.-M. Steyskal, H. Krenn, R. Würschum, Magneto-Ionic Switching of Superparamagnetism, Small 15, 1904523 (2019), https://doi.org/10.1002/smll.201904523