Scientific Highlights
Concept of a multichannel spin-resolving electron analyzer based on Mott scattering
The spin of electron plays a crucial role in many physical phenomena, ranging from the obvious example of magnetism, via novel materials for spintronics applications, to high-temperature superconductivity. Spin- and angle-resolved photoelectron spectroscopy (SARPES) gives the most direct access to the spin aspects of the electronic structure, but the one-channel detection principle of all presently available SARPES spectrometers severely limits their efficiency. A team of Swiss and Russian scientists has developed a revolutionary concept of a multichannel electron spin detector based on Mott scattering as the spin selective process and imaging-type electron optics.
Mutual Independence of Critical Temperature and Superfluid Density under Pressure in Optimally Electron-Doped Superconducting LaFeAsO1−xFx
The superconducting properties of LaFeAsO1−xFx under conditions of optimal electron doping are investigated upon the application of external pressure up to ∼23 kbar. Measurements of muon-spin spectroscopy and dc magnetometry evidence a clear mutual independence between the critical temperature Tc and the low-temperature saturation value for the ratio ns/m* (superfluid density over effective band mass of Cooper pairs).
Spin-stripe phase in a frustrated zigzag spin-1/2 chain
In strongly correlated electron systems periodic modulations on the nano-scale have typically been associated with competition between short- and long-range interactions, for example, between exchange and dipole-dipole interactions in the case of ferromagnetic thin films. Here we show that spin-stripe textures may develop also in antiferromagnets, where long-range dipole-dipole magnetic interactions are absent.
Spin-stripe phase in a frustrated zigzag spin-1/2 chain
Motifs of periodic modulations are encountered in a variety of natural systems, where at least two rival states are present. In strongly correlated electron systems, such behaviour has typically been associated with competition between short- and long-range interactions, for example, between exchange and dipole-dipole interactions in the case of ferromagnetic thin films.
Controllable Broadband Absorption in the Mixed Phase of Metamagnets
Combination of neutron scattering, muon spin relaxation, specific heat, ac and dc magnetization measurements, and electron magnetic resonance, reveals the ability of metamagnetic materials to absorb the electromagnetic radiation in an extremely broad frequency range.
Catalytically Active and Spectator Ce3+ in Ceria-Supported Metal Catalysts
Identification of active species and the rate-determining reaction steps are crucial for optimizing the performance of oxygen-storage materials, which play an important role in catalysts lowering automotive emissions, as electrode materials for fuel cells, and as antioxidants in biomedicine. We demonstrated that active Ce3+ species in a ceria-supported platinum catalyst during CO oxidation are short-lived and therefore cannot be observed under steady-state conditions.
Catalytically Active and Spectator Ce3+ in Ceria-Supported Metal Catalysts
Using time-resolved resonant X-ray emission spectroscopy, we quantitatively correlated the initial rate of Ce3+ formation under transient conditions to the overall rate of CO oxidation under steady-state conditions and showed that ceria reduction is a kinetically relevant step in CO oxidation, whereas a fraction of Ce3+ was present as spectators.
PSI-DESY Collaboration Delivers First Photonics Component for SwissFEL
The Photon Beam Intensity Gas (PBIG) monitor arrived at PSI at the end of May, and will be one of the first photonics components to be installed in the new SwissFEL facility.The gas-based photon beam position and intensity monitor is a device originally developed by Dr. Kai Tiedtke and his team at the Deutsches Elektronen-Synchrotron (DESY) for the non-destructive measurement of an X-ray FEL's beam position and flux. The accurate measurement of these variables is necessary due to the stochastic nature of the self-amplified spontaneous emission (SASE) process which can create jitters in the position and flux of the FEL beam on a shot-to-shot basis. The device has been developed and adapted to fit the SwissFEL parameters in a PSI-DESY collaboration over the course of two years.
Magnetoelectric domain control in multiferroic TbMnO3
The manipulation of domains by external fields in ferroic materials is of major interest for applications. In multiferroics with strongly coupled magnetic and electric order, however, the magnetoelectric coupling on the level of the domains is largely unexplored. We investigated the field-induced domain dynamics of TbMnO3 in the multiferroic ground state and across a first-order spin-flop transition.
Single- (K) and Double-Electron Excitation (KLII&III) XANES Spectra of α-Alumina and Aqueous Al3+•(H2O)6
X-ray absorption spectroscopy (XAS) probes the local environment around an atom by study of the local photoelectron’s scattering. Multielectron excitations become more important at higher x-ray dose, which are used for examples in x-FEL experiments. Here we demonstrate that multielectron excitations, observed in the Al K-edges EXAFS spectra can be used to derive structural information.