23 research outputs found
Hole-depletion of ladders in SrCuO induced by correlation effects
The hole distribution in SrCuO is studied by low
temperature polarization dependent O K Near-Edge X-ray Absorption Fine
Structure measurements and state of the art electronic structure calculations
that include core-hole and correlation effects in a mean-field approach.
Contrary to all previous analysis, based on semi-empirical models, we show that
correlations and antiferromagnetic ordering favor the strong chain
hole-attraction. For the remaining small number of holes accommodated on
ladders, leg-sites are preferred to rung-sites. The small hole affinity of
rung-sites explains naturally the 1D - 2D cross-over in the phase diagram of
(La,Y,Sr,Ca)CuOComment: 6 pages, 8 figure
Emergent c-axis magnetic helix in manganite-nickelate superlattices
The nature of the magnetic order in (La2/3Sr1/3MnO3)9/(LaNiO3)3 superlattices
is investigated using x-ray resonant magnetic reflectometry. We observe a new
c-axis magnetic helix state in the (LaNiO3)3 layers that had never been
reported in nickelates, and which mediates the ~130deg magnetic coupling
between the ferromagnetic (La2/3Sr1/3MnO3)9 layers, illustrating the power of
x-rays for discovering the magnetic state of complex oxide interfaces. Resonant
inelastic x-ray scattering and x-ray absorption spectroscopy show that Ni-O
ligand hole states from bulk LaNiO3 are mostly filled due to interfacial
electron transfer from Mn, driving the Ni orbitals closer to an atomic-like 3d8
configuration. We discuss the constraints imposed by this electronic
configuration to the microscopic origin of the observed magnetic structure. The
presence of a magnetic helix in (La2/3Sr1/3MnO3)9/(LaNiO3)3 is crucial for
modeling the potential spintronic functionality of this system and may be
important for designing emergent magnetism in novel devices in general.Comment: 7 pages, 5 figure
Resonant inelastic x-ray scattering data for Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates
Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates are intriguing
candidates for mimicking the properties of high-temperature superconducting
cuprates. The degree of similarity between these nickelates and cuprates has
been the subject of considerable debate. Resonant inelastic x-ray scattering
(RIXS) has played an important role in exploring their electronic and magnetic
excitations, but these efforts have been stymied by inconsistencies between
different samples and the lack of publicly available data for detailed
comparison. To address this issue, we present open RIXS data on La4Ni3O10 and
La4Ni3O8.Comment: Data descriptor article; accepted in Scientific Data; 8 pages; 6
figure
Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL
Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very promising technique that can be employed at X-ray Free Electron Lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here we present a dedicated setup for soft X-rays available at the Spectroscopy & Coherent Scattering (SCS) instrument at the European X-ray Free Electron Laser (EuXFEL). It consists of a beam-splitting off-axis zone plate (BOZ) used in transmission to create three copies of the incoming beam, which are used to measure the transmitted intensity through the excited and unexcited sample, as well as to monitor the incoming intensity. Since these three intensity signals are detected shot-by-shot and simultaneously, this setup allows normalized shot-by-shot analysis of the transmission. For photon detection, the DSSC imaging detector, which is capable of recording up to 800 images at 4.5 MHz frame rate during the FEL burst, is employed and allows approaching the photon shot-noise limit. We review the setup and its capabilities, as well as the online and offline analysis tools provided to users
Localized electronic excitations in NiO studied with resonant inelastic X-ray scattering at the Ni M threshold: Evidence of spin flip
We studied the neutral electronic excitations of NiO localized at the Ni sites by measuring the resonant inelastic x-ray scattering (RIXS) spectra at the Ni M-2,M-3 edges. The good energy resolution allows an unambiguous identification of several spectral features due to dd excitations. The dependence of the RIXS spectra on the excitation energy gives evidence of local spin flip and yields a value of 125 +/- 15 meV for the antiferromagnetic exchange interaction. Accurate crystal field parameters are also obtained
Magnetic and Electronic Properties of GdNiAl Intermetallic Compounds
X-ray photoelectron spectroscopy and magnetic susceptibility of GdNi, GdNiAl, GdNiAl and GdNiAl are reported. The magnetic state of Ni 3d-electrons strongly depends on the crystallographic structure of the compounds, showing spin fluctuations in GdNi and GdNiAl, a similar behavior with that of metallic Ni in GdNiAl and a filled 3d-band in GdNiAl