Data Science

Recent advances in fabrication techniques to create mesoscopic 3D structures have led to significant developments in a variety of fields including biology, photonics, and magnetism. Further progress in these areas benefits from their full quantitative and structural characterization.

Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core.

Only three elements are ferromagnetic at room temperature: the transition metals iron, cobalt and nickel. The Stoner criterion explains why iron is ferromagnetic but manganese, for example, is not, even though both elements have an unfilled 3d shell and are adjacent in the periodic table: according to this criterion, the product of the density of states and the exchange integral must be greater than unity for spontaneous spin ordering to emerge.

In the generic phase diagram of heavy fermion systems, tuning an external parameter such as hydrostatic or chemical pressure modifies the superconducting transition temperature. The superconducting phase forms a dome in the temperature-tuning parameter phase diagram, which is associated with a maximum of the superconducting pairing interaction. Proximity to antiferromagnetism suggests a relation between the disappearance of antiferromagnetic order and superconductivity.

Magnetic skyrmions are tiny, magnetic-spin vortices that can emerge in magnetic materials. Due to their nanometric size, skyrmions could be used to build extremely high density memory spintronics devices. However, stable skyrmions are not easy to find and control, and are usually only observed well below room temperature.

The horizontal and vertical offset mirrors are key optical elements for the SwissFEL ARAMIS Beamline. The offset mirrors for example, are used to deflect and steer the x-ray beam into one of the end stations. As the sample position is about 60m from the mirror, very high demands are put on the mirror positioning system in order to deflect the x-ray beam on to the sample with a micro-meter precision. Therefore precise positioning of the mirrors is required, with specifications to move a load of up to 200kg by steps as small as 0.3µm. Not just the positioning must be precise, but also the stability for short term vibrations and long term drifts must be superior.

Very small superparamagnetic iron oxide nanoparticles were characterized by innovative synchrotron X-ray total scattering methods and Debye function analysis, developed at the X04SA Materials Science beamline of SLS.

Skyrmions, topologically protected vortex-like nanometric spin textures in magnets, have been attracting increasing attention for emergent electromagnetic responses and possible technological applications for spintronics. In particular, metallic magnets with chiral and cubic/tetragonal crystal structure may have high potential to host skyrmions that can be driven by low electrical current excitation.

Using XAS it was demonstrated that carbon acts as an activity booster for Ba0.5Sr0.5Co0.8Fe0.2O3 oxygen reduction and evolution electrocatalyst promoting change of cobalt oxidation state.

We employ resonant soft x-ray diffraction to individually study the magnetic ordering of the Mn and the Tm sublattices in single-crystalline films of orthorhombic (o−)TmMnO₃. The same magnetic ordering wave vector of (0q0) with q≈0.46 is found for both ionic species, suggesting that the familiar antiferromagnetic order of the Mn ions induces a magnetic order on the Tm unpaired 4f electrons.

In pulsed laser deposition the use of a rectangular or elliptical beam spot with a non 1:1 aspect ratio leads to the so called flip-over effect. Here, the longest dimension of the laser spot results in the shortest direction of plasma plume expansion.

The surface-induced changes of the oxidation state and magnetic properties of Mn ion clusters have been probed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism.

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.

A research team led by scientists from the Swiss Light Source has for the first time established three-dimensional (3D) electronic structure of the perovskite compound La1−xSrxMnO3 connected with its colossal magnetoresistance. Instrumental for this study has been the use of the new experimental technique of soft-x-ray ARPES, available at the ADRESS beamline, with its intrinsically sharp definition of 3D electron momentum.

The superconducting properties of LaFeAsO_1−xF_x 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 T_c and the low-temperature saturation value for the ratio n_s/m^* (superfluid density over effective band mass of Cooper pairs).

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.

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.

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.

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.

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.

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.

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.