From Dublin to Berlin as a Humboldt Research Fellow
Dr. Katarzyna Siewierska joins the group of Prof. Alexander Föhlisch as a postdoctoral Humboldt Research fellow. © Privat
Dr. Katarzyna Siewierska joins the group of Prof. Alexander Föhlisch as a postdoctoral Humboldt Research fellow. She has earned her PhD at Trinity College in Dublin, Ireland, and plans in the next two years to explore the electronic structure and spin dynamics of half-metallic thin films at BESSY II. Understanding these spintronic materials better may pave the way for more energy efficient data storage technologies.
Katarzyna Siewierska describes her project herself very clearly:
A dream material for spintronics would have low/zero net moment, no stray fields, high resonance frequency, low damping and be 100 % spin polarised, combining the best features of a metallic ferromagnet and an antiferromagnet. Such materials have the potential to revolutionise magnetic data storage and data transfer. They are called zero moment half-metals (ZMHM). This new material class was theoretically predicted in 1995, but it took almost 20 years before the first member, Mn2RuxGa, was demonstrated in 2014.
Up to now, the few other examples of ZMHMs are all Mangan-based Heusler alloys, revealing the critical role of Mangan for obtaining the uniquely desirable combination of properties. It is of great research interest to understand why this is so.
Synchrotron radiation-based techniques provide important insights into the electronic and magnetic properties of spintronic materials due to their sensitivity to spin and crystal structure, coupled with element specificity.
In this work we will combine the expertise of researchers at BESSY II in resonant inelastic X-ray scattering (RIXS) with the high quality ZMHM thin films I fabricated and studied at Trinity College Dublin (TCD) during my thesis. The goal is to confirm the half-metallic band structure of MRG, explore the spin-lattice relaxation and investigating magnon excitations to obtain information about their dispersion and the energy of ferrimagnetic resonance modes.
- A new way to control the magnetic properties of rare earth elementsThe special properties of rare earth magnetic materials are due to the electrons in the 4f shell. Until now, the magnetic properties of 4f electrons were considered almost impossible to control. Now, a team from HZB, Freie Universität Berlin and other institutions has shown for the first time that laser pulses can influence 4f electrons- and thus change their magnetic properties. The discovery, which was made through experiments at EuXFEL and FLASH, opens up a new way to data storage with rare earth elements.
- HZB magazine lichtblick - the new issue is out!In his search for the perfect catalyst, HZB researcher Robert Seidel is now getting a tailwind – thanks to a ERC Consolidator Grant. In the cover story, we explain why the X-ray source BESSY II plays an important role for his research.
- BESSY II shows how solid-state batteries degradeSolid-state batteries have several advantages: they can store more energy and are safer than batteries with liquid electrolytes. However, they do not last as long and their capacity decreases with each charge cycle. But it doesn't have to stay that way: Researchers are already on the trail of the causes. In the journal ACS Energy Letters, a team from HZB and Justus-Liebig-Universität, Giessen, presents a new method for precisely monitoring electrochemical reactions during the operation of a solid-state battery using photoelectron spectroscopy at BESSY II. The results help to improve battery materials and design.