Annual Report 2011 / 2012 - E21 - Technische Universität München

Preface 1
Preface
In the name of all members of the Institute on Strongly Correlated Electron Systems (formerly Institute E21)
at the Physik-Department of the Technical University of Munich we are pleased to present the biannual report
2011/12 highlighting some of the exciting research performed during the last two years. Our research
concentrated mostly on the effects of strong correlations in magnetic and superconducting materials and on
technical developments for our beam lines at the neutron source FRM II as well as our crystal growth and low
temperature laboratories.
In our scientific studies we succeeded to achieve again several major breakthroughs. As in the years before
the non-centrosymmetric B20 compounds provided thereby a “drosophila” comprising the observation of giant
spin torque effects and the identification of a fluctuation-induced first-order phase transition as predicted by
Brasovskii over 25 years ago. As part of the projects funded by the Collaborative Transregional Research
Network (TRR 80) we succeeded to install a new beam line for ACAR (angular correlation of the annihilation
radiation) by the positron group at NEPOMUC that allows us to determine the momentum density of the
electrons even in multicomponent materials and at high temperature. ACAR will provide complementary
information to interpret the results from our bulk and microscopic techniques. In addition, we conducted first
in-situ reflectivity measurements of the preparation of magnetic monolayers using polarized neutrons at the
beamline REFSANS at FRM II.
Despite these successes our neutron scattering studies were somewhat constrained by the long-planned
shutdown of FRM II in 2011, which was efficiently used to upgrade the beamlines of our institute. At the
positron facility NEPOMUC the beam tube and the inserted positron source were exchanged due to the burnup
of the gamma producing cadmium cap. The new source has a longer live time and the positron beams are
again operational with even higher quality. The diffractometer MIRA 2 is now equipped with a graphite analyser
making high resolution cold triple-axis spectroscopy from small samples possible. The primary spectrometer of
RESEDA could be improved greatly by moving the velocity selector from the TREFF monochromator shielding
to its own housing. Moreover, the installation of a new generation of RF-coils offers now Larmor diffraction
at RESEDA providing an unprecedented momentum resolution. In addition, members of our institute actively
contributed to design studies for future beam lines at the European Spallation Source ESS.
An unexpected constraint of our work at FRM II was caused by technical problems at the neutron guides
NL5 and NL6, which severely limited the number of operational days of MIRA and RESEDA. Further, the
relocation of the imaging beamline ANTARES due to the installation of the neutron guides for the fundamental
physics beam line PERC precluded its use altogether. Here we thank the imaging group at PSI for providing
beam time at the ICON beam line at SINQ.
We would finally like to thank all funding agencies, namely DFG, BMBF, and the European Union under
NMI3 for their continued generous financial support. As a highlight and a result of the highly successful series
of experimental studies of topological spin textures at our institute, we are now even able to conduct a research
program on topological spin solitons for information technology in the framework of an Advanced Grant of the
European Research Council.
Last but not least, we congratulate Dr. Christoph Hugenschmidt for completing his habilitation in the field
of positron physics and the large number of research students for completing their bachelor, master, diploma
and doctoral thesis. It is with great pleasure and a good deal of pride that we thank all members of our institute
for their enthusiastic efforts in teaching and research. Without their outstanding commitment it would not have
been possible to advance the large number of highly ambitious projects. The unique combination of hard work
and ‘intense’ social events (mostly initiated by our young scientists) have been essential in creating an excellent
atmosphere for everybody.
Garching, February 2013
Peter Böni Christian Pfleiderer Klaus Schreckenbach