A compact spectrometer for medium‐resolution resonant and non‐resonant X‐ray emission spectroscopy in von Hámos geometry is described. The main motivation for the design and construction of the ...spectrometer is to allow for acquisition of non‐resonant X‐ray emission spectra while measuring non‐resonant X‐ray Raman scattering spectra at beamline ID20 of the European Synchrotron Radiation Facility. Technical details are provided and the performance and possible use of the spectrometer are demonstrated by presenting results of several X‐ray spectroscopic methods on various compounds.
A new X‐ray spectrometer in von Hamos geometry for parallel X‐ray Raman scattering and X‐ray emission spectroscopy is available at the inelastic X‐ray scattering beamline ID20 of the ESRF.
A compilation of procedures for planning and performing X‐ray Raman scattering (XRS) experiments and analyzing data obtained from them is presented. In particular, it is demonstrated how to predict ...the overall shape of the spectra, estimate detection limits for dilute samples, and how to normalize the recorded spectra to absolute units. In addition, methods for processing data from multiple‐crystal XRS spectrometers with imaging capability are presented, including a super‐resolution method that can be used for direct tomography using XRS spectra as the contrast. An open‐source software package with these procedures implemented is also made available.
An algorithm to simultaneously increase the spatial and statistical accuracy of X‐ray Raman scattering (XRS) based tomographic images is presented. Tomography that utilizes XRS spectroscopy signals ...as a contrast for the images is a new and promising tool for investigating local atomic structure and chemistry in heterogeneous samples. The algorithm enables the spatial resolution to be increased based on a deconvolution of the optical response function of the spectrometer and, most importantly, it allows for the combination of data collected from multiple analyzers and thus enhances the statistical accuracy of the measured images.
An algorithm to simultaneously increase the spatial and statistical accuracy of X‐ray Raman scattering based tomographic images is presented.
A method to separate the non‐resonant inelastic X‐ray scattering signal of a micro‐metric sample contained inside a diamond anvil cell (DAC) from the signal originating from the high‐pressure sample ...environment is described. Especially for high‐pressure experiments, the parasitic signal originating from the diamond anvils, the gasket and/or the pressure medium can easily obscure the sample signal or even render the experiment impossible. Another severe complication for high‐pressure non‐resonant inelastic X‐ray measurements, such as X‐ray Raman scattering spectroscopy, can be the proximity of the desired sample edge energy to an absorption edge energy of elements constituting the DAC. It is shown that recording the scattered signal in a spatially resolved manner allows these problems to be overcome by separating the sample signal from the spurious scattering of the DAC without constraints on the solid angle of detection. Furthermore, simple machine learning algorithms facilitate finding the corresponding detector pixels that record the sample signal. The outlined experimental technique and data analysis approach are demonstrated by presenting spectra of the Si L2,3‐edge and O K‐edge of compressed α‐quartz. The spectra are of unprecedented quality and both the O K‐edge and the Si L2,3‐edge clearly show the existence of a pressure‐induced phase transition between 10 and 24 GPa.
Spatially resolved signal collection enhances data quality of non‐resonant inelastic X‐ray scattering experiments dramatically. This new technique is demonstrated by presenting data from the O K‐ and Si L2,3‐edge of SiO2 α‐quartz at high pressure.
We report the doping dependence of the ground state of A-site ordered manganites below and above half doping. Energy and polarization dependence of the orbital reflection, taken by resonant ...soft-x-ray powder diffraction, at both Mn L(2,3) and O K edges, provides direct evidence for orbital order at Mn(3+) and oxygen sites and absence of Zener polaron formation. For x > or = 0.2 anomalous melting of the orbital order is observed, which is coupled neither to magnetic ordering nor to a structural transition, indicating a two-dimensional character of the interactions.
The performance of manganite-based magnetic tunnel junctions (MTJs) has suffered from reduced magnetization present at the junction interfaces that is ultimately responsible for the spin polarization ...of injected currents; this behavior has been attributed to a magnetic “dead layer” that typically extends a few unit cells into the manganite. X-ray magnetic scattering in resonant conditions (XRMS) is one of the most innovative and effective techniques to extract surface or interfacial magnetization profiles with subnanometer resolution, and has only recently been applied to oxide heterostructures. Here we present our approach to characterizing the surface and interfacial magnetization of such heterostructures using the XRMS technique, conducted at the BEAR beamline (Elettra synchrotron, Trieste). Measurements were carried out in specular reflectivity geometry, switching the left/right elliptical polarization of light as well as the magnetization direction in the scattering plane. Spectra were collected across the Mn L
2,3 edge for at least four different grazing angles to better analyse the interference phenomena. The resulting reflectivity spectra have been carefully fit to obtain the magnetization profiles, minimizing the number of free parameters as much as possible. Optical constants of the samples (real and imaginary part of the refractive index) in the interested frequency range are obtained through absorption measurements in two magnetization states and subsequent Kramers–Krönig transformation, allowing quantitative fits of the magnetization profile at different temperatures. We apply this method to the study of air-exposed surfaces of epitaxial La
2/3Sr
1/3MnO
3 (0
0
1) films grown on SrTiO
3 (0
0
1) substrates.
We have determined the optical constants at the 2p edges of iron by measuring the Bragg scattering from a Fe/V superlattice using elliptically polarized photons whose energies were tuned across the ...Fe 2p resonances (700-730 eV). The analysis of the Bragg
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