Welcome to the Homepage of Prof. Dr. Claudia Felser

comCIGS II: Ab initio simulation of interfacial phenomena in Cu(In,Ga)Se2 solar cells

Doktorarbeit / PhD Research Position:Atomic scale mechanisms at surfaces andinterfaces in thin films solar cells

Chemist receives high distinction for her research into new materials Chemikerin erhält hohe fachliche Auszeichnung für die Erforschung von neuen Materialien

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Die erst vor wenigen Jahren entdeckte Materialklasse der Topologischen Isolatoren zeichnen sich durch ihre herausragende Eigenschaft aus, im Innern elektrisch isolierend zu sein, an der Oberfläche jedoch leitende Zustände auszubilden. Das Besondere an topologischen Isolatoren ist die extreme Stabilität ihrer Oberflächenzustände.

Gasteditoren Claudia Felser, Shoucheng Zhang und Binghai Yan von der Johannes Gutenberg-Universität Mainz und dem Max-Planck-Institut in Dresden fangen den aktuellen Forschungsstand bezüglich Eigenschaften und Anwendungen dieser Materialklasse in einer erstklassigen Momentaufnahme ein. 

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• Heusler-Permanentmagnete ohne Seltenerdmetalle 
• Heusler Verbindungen für Spin-Transfer-Torque-(STT)-Anwendungen
• Magnetokalorische Heusler Verbindungen 

Since several years Bob Cava has a strong collaboration with Mainz, to further strengthen this collaboration he has received now the Johannes Gutenberg lecturer award.
Lesslie Schoop a graduate student of the graduate school of excellence has successfully apply for the Ph.D program in Princeton. She will work in Bob Cava’s group searching for new superconductors jointly with Moment group in Mainz.

(Foto by Eric Lichtenstein)
from left to right: Claudia Felser, Bob Cava, Lesslie Schoop)

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Heusler compounds are a remarkable class of intermetallic materials with 1:1:1 (often called Half- Heusler) or 2:1:1 composition comprising more than 1500 members. Today, more than a century after their discovery by Fritz Heusler, they are still a field of active research. New properties and potential fields of applications emerge constantly; the prediction of topological insulators is the most recent example. Surprisingly, the properties of many Heusler compounds can easily be predicted by the valence electron count. Their extremely flexible electronic structure offers a toolbox which allows the realization of demanded but apparently contradictory functionalities within one ternary compound. Devices based on multifunctional properties, i.e. the combination of two or more functions such as superconductivity and topological edge states will revolutionize technological applications. The subgroup of more than 250 semiconductors is of high relevance for the development of novel materials for energy technologies. Their band gaps can readily be tuned from zero to ~4 eV by changing the chemical composition. Thus, great interest has been attracted in the fields of thermoelectrics and solar cell research. The wide range of their multifunctional properties is also reflected in extraordinary magneto-optical, magnetoelectronic, and magnetocaloric properties. The most prominent example is the combination of magnetism and exceptional transport properties in spintronic devices. To take advantage of the extremely high potential of Heusler compounds simple rules for the understanding of the structure, the electronic structure and the relation to the properties are reviewed.  

Online version:  Graf T, Felser C, Parkin SS. Simple Rules for the Understanding of Heusler Compounds, Progress in Solid State Chemistry (2011),
doi: 10.1016/j.progsolidstchem.2011.02.001
A short version has appeared in: IEEE Transaction on Magnetics 47, 2011 367

Die Deutsche Forschungsgemeinschaft (DFG) hat Dr. Sabine Wurmehl in ihr renommiertes Emmy-Noether-Programm zur Förderung des wissenschaftlichen Nachwuchses aufgenommen. Das Projekt ermöglicht es Frau Dr. Wurmehl, für bis zu fünf Jahre eine von der DFG geförderte, unabhängige Forschergruppe mit drei Doktoranden am Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden (IFW) zu führen. Der inhaltliche Schwerpunkt liegt in Materialien für die Spintronik.

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Website ASPIMAT http://www.aspimatt.de

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Electronic and magnetic phase diagram of ^ß-Fe_1.01Se with superconductivity at 36.7 K under pressure

The discovery of new high-temperature superconductors based on FeAs has led to a new 'gold rush' in high-T_C superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach T_C values up to 55 K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of ^ß-Fe1.01Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7 K under an applied pressure of 8.9 GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as T_C rises, owing to a collapse of the separation between the Fe₂Se₂ layers. No static magnetic ordering is observed for the whole p–T phase diagram. We also report that at higher pressures (starting around 7 GPa and completed at 38 GPa), Fe_1.01Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.

doi:10.1038/nmat2491

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