Data Science

We present neutron scattering data on the structure and dynamics of melts from polyethylene oxide rings with molecular weights up to ten times the entanglement mass of the linear counterpart. The data reveal a very compact conformation displaying a structure approaching a mass fractal, as hypothesized by recent simulation work. The dynamics is characterized by a fast Rouse relaxation of subunits (loops) and a slower dynamics displaying a lattice animal-like loop displacement.

Strain is a leading candidate for controlling magnetoelectric coupling in multiferroics. Here, we use x-ray diffraction to study the coupling between magnetic order and structural distortion in epitaxial films of the orthorhombic (o-) perovskite LuMnO₃. An antiferromagnetic spin canting in the E-type magnetic structure is shown to be related to the ferroelectrically induced structural distortion and to a change in the magnetic propagation vector.

Magnetic shape-memory Heusler alloys are multiferroics stabilized by the correlations between electronic, magnetic, and structural order. To study these correlations we use time-resolved x-ray diffraction and magneto-optical Kerr effect experiments to measure the laser induced dynamics in a Heusler alloy Ni2MnGa film and reveal a set of time scales intrinsic to the system.

We present a direct spectroscopic observation of a shallow hydrogenlike muonium state in SrTiO₃ which confirms the theoretical prediction that interstitial hydrogen may act as a shallow donor in this material. The formation of this muonium state is temperature dependent and appears below ∼70 K. From the temperature dependence we estimate an activation energy of ∼50 meV in the bulk and ∼23 meV near the free surface. The field and directional dependence of the muonium precession frequencies further supports the shallow impurity state with a rare example of a fully anisotropic hyperfine tensor.

We implement a systematic effective field theory approach to the benchmark process μ → eγ, performing automated one-loop computations including dimension 6 operators and studying their anomalous dimensions. We obtain limits on Wilson coefficients of a relevant subset of lepton-flavour violating operators that contribute to the branching ratio μ → eγ at one-loop.

Discovering fundamentally new ways to manipulate magnetic spins is crucial for research into advanced technologies. Magnetic Skyrmions, which are topologically stable whirls of magnetic spins, are promising candidates for new device components since those found in metallic host materials can be manipulated using electric currents.

The interaction with light weakens the superconducting ground state in classical superconductors. The situation in cuprate superconductors is more complicated: illumination increases the charge carrier density, a photo-induced effect that persists below room temperature. Furthermore, systematic investigations in underdoped YBa₂Cu₃O_6+x (YBCO) have shown an enhanced critical temperature T_c. Until now, studies of photo-persistent conductivity (PPC) have been limited to investigations of structural and transport properties, as well as the onset of superconductivity.

Plasma chemistry and scattering strongly affect the congruent, elemental transfer during pulsed laser deposition of target metal species in an oxygen atmosphere. Studying the plasma properties of La_0.6Sr_0.4MnO₃, we demonstrate for as grown La_0.6Sr_0.4MnO_3-δ films that a congruent transfer of metallic species is achieved in two pressure windows: ∼10⁻³ mbar and ∼2 × 10⁻¹ mbar.

The need for reducing the operating temperature of solid-oxide fuel cells (SOFCs) imposed by cost reduction has pushed significant progress in fundamental understanding of the individual components, as well as materials innovation and device engineering. Proton-conducting oxides have emerged as potential alternative electrolyte materials to oxygen-ion conducting oxides for operation at low and intermediate temperatures.

Using angle-resolved photoemission spectroscopy, we show that the recently discovered surface state on SrTiO₃ consists of nondegenerate t_2g states with different dimensional characters.

Strontium titanate, SrTiO3, is an important material for the realization of next-generation electronic devices. A famous example is the interface of LaAlO3 grown on SrTiO3, which is metallic and magnetic at its interface, even though the individual compounds are insulating and nonmagnetic in bulk form. The physics behind how novel interface states form on SrTiO3 - and how they become endowed with such surprising properties - is not well understood.

EuTiO₃, which is a G-type antiferromagnet below T_N = 5.5 K, has some fascinating properties at high temperatures, suggesting that macroscopically hidden dynamically fluctuating weak magnetism exists at high temperatures. This conjecture is substantiated by magnetic field dependent magnetization measurements, which exhibit pronounced anomalies below 200 K becoming more distinctive with increasing magnetic field strength. Additional results from muon spin rotation experiments provide evidence for weak fluctuating bulk magnetism induced by spin-lattice coupling which is strongly supported in increasing magnetic field.

Partially amorphous La_0.6Sr_0.4CoO_3-δ (LSC) thin-film cathodes are fabricated using pulsed laser deposition and are integrated in free-standing micro-solid oxide fuel cells (micro-SOFC) with a 3YSZ electrolyte and a Pt anode. A low degree of crystallinity of the LSC layers is achieved by taking advantage of the miniaturization of the cells, which permits low-temperature operation (300–450 °C).

The smaller pixel size, high frame rate, and high dynamic range of next-generation photon counting pixel detectors expedites measurements based on coherent diffractive imaging (CDI). The latter comprises methods that exploit the coherence of X-ray synchrotron sources to replace imaging optics by reconstruction algorithms. Researchers from the Paul Scherrer Institut have recently demonstrated fast CDI image acquisition above 25,000 resolution elements per second using an in-house developed Eiger detector. This rate is state of the art for diffractive imaging and even on a par with the fastest scanning X-ray transmission instruments. High image throughput is of crucial importance for both materials and biological sciences for studies with representative population sampling.