Topics
Spintronics
In spintronics the electron spin is utilized to store and process information. The presently most common example are hard disc drives (see figure). The picosecond time structure of synchrotron radiation allows us to stroboscopically image the magnetization reversal in magnetic data storage media following a short magnetic field pulse. High resolution photoelectron spectroscopy provides information about spin dependent scattering responsible for magnetoresistance.
Ultrafast Magnetism
Heating of a ferromagnet above its Curie temperature leads to an angular momentum transfer to the lattice similar to the static Einstein de Haas effect (see figure). We use femtosecond soft x-ray pulses form the BESSY II femtoslicing source for observing energy and angular momentum redistibution after heating the bits of a magnetic storage device by a femtosecond laser pulse. This has implications for determining the ultimate writing speed of magnetic data storage devices.
Electron & Spin Correlations in Complex Materials
Many properties of modern complex materials are determined by the strong coupling of electronic degrees of freedom with spin and lattice excitations. High temperature superconductivity in cuprates and iron-pnictides where the formation of Cooper pairs is thought to be mediated by spin excitations is one example. We strive at using the complementarity of high resolution angle resolved photoemission spectroscopy (the figure shows a Fermi surface of a cuprate superconductor) and neutron scattering to probe exactly this interaction.
Interface Magnetism
Interfaces between different magnetic or magnetic / non-magnetic materials often determine device properties. The probably best known example is the giant magneto resistance effect in spin valves which is related to spin dependent scattering processes. However, also effects such as exchange bias and the magnetic anisotropy originate at or can be dominated by interfaces. The properties of buried interfaces are probed by resonant magnetic x-ray scattering and standing x-ray wave spectroscopy (see figure).
Nano Magnetism
Magnetism is usually considered to be dominated by the electron spin. However, also the orbital electronic motion around the nucleus contributes to the magnetic moment. This, so called, orbital moment determines the orientation of the electron spins. The dynamics of individual nanostructures is probed using spectromicroscopy (the figure shows 10nm CoO clusters in yellow on a Si substrate). Scattering techniques are used to determine properties of nanostructure ensembles.
