7 research outputs found
Local tetragonal distortion in La_{0.7}Sr_{0.3}MnO_3 strained thin films probed by x-ray absorption spectroscopy
We report on an angular resolved X-ray Absorption Spectroscopy study of
thin films epitaxially grown by pulsed laser
deposition on slightly mismatched substrates which induce tensile or
compressive strains. XANES spectra give evidence of tetragonal distortion
within the octahedra, with opposite directions for tensile and
compressive strains. Quantitative analysis has been done and a model of
tetragonal distortion reflecting the strain has been established. EXAFS data
collected in plane for tensile substrate confirm the change in the
average bond distance and the increase of length matching with the
enlargement of the cell parameter. From these results we conclude that there is
no significant change in the angle. Our observations conflict with
the scenarios which this angle is the main driving parameter in the sensitivity
of manganite films properties to external strains and suggest that the
distortion within the octahedra plays a key role in the modification of the
transport and magnetic properties.Comment: 8 pages, 6 figure
Interface-driven phase separation in multifunctional materials: the case of GeMn ferromagnetic semiconductor
We use extensive first principle simulations to show the major role played by
interfaces in the mechanism of phase separation observed in semiconductor
multifunctional materials. We make an analogy with the precipitation sequence
observed in over-saturated AlCu alloys, and replace the Guinier-Preston zones
in this new context. A new class of materials, the phases, is proposed
to understand the formation of the coherent precipitates observed in the GeMn
system. The interplay between formation and interface energies is analyzed for
these phases and for the structures usually considered in the literature. The
existence of the alpha phases is assessed with both theoretical and
experimental arguments
Étude du transport dépendant du spin dans des nanostructures à base de manganite
Half-metals due to their high spin polarization play a key role in spintronics. We have chosen to study one of them, the manganite La0.7Sr0.3MnO3 (LSMO). Spin-dependent transport properties were studied using epitaxial LSMO layer. It was required to study also epitaxy and strain relaxation of these films. Induced modifications of magnetic properties of LSMO in these films is also addressed. Magnetotransport properties of heterojunctions formed in oxyde superlattices of LSMO/SrTiO3 (STO) and in hybrid trilayers of LSMO/STO/Co0.88Fe0.12 are studied. Both heterojunctions shows premature decrease of the magnetoresistives effects in temperature. This behavior is linked to premature decrease of magnetism at surfaces of LSMO. Therefore, profile of magnetism and oxygen stoichiometry through the thickness of LSMO films is investigated using polarized neutron reflectometry and X-ray reflectivity.Les demi-métaux, du fait de leur forte polarisation en spin jouent un rôle clef dans l'électronique de spin. Nous avons choisi d'étudier l'un d'eux : le manganite La0.7Sr0.3MnO3 (LSMO). Nous avons étudié les propriétés de transport dépendant du spin dans des hétérostructures à base de couches épitaxiales de LSMO. Il était ainsi requis d'étudier aussi l'épitaxie, la relaxation des contraintes et les modification de l'anisotropie magnétique du LSMO sous contraintes. L'étude des propriétés de magnétotransport de jonctions formées à partir de superréseaux de LSMO/SrTiO3 (STO) et à partir de tricouches de LSMO/STO/Co0.88Fe0.12 a montré des dépendances thermiques rapides des effets magnétorésistifs en température. Ces effets étant liés au magnétisme de surface du LSMO, nous avons donc effectué des mesures de magnétisme et de stoechiométrie en oxygène spatialement résolues à l'échelle du nanomètre en utilisant la réflectométrie de neutrons polarisés et la réflectivité X
Etude du transport dépendant du spin dans des nanostructures à base de manganite
GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF
Continuous scanning for Bragg coherent X-ray imaging
We explore the use of continuous scanning during data acquisition for Bragg coherent diffraction imaging, i.e., where the sample is in continuous motion. The fidelity of continuous scanning Bragg coherent diffraction imaging is demonstrated on a single Pt nanoparticle in a flow reactor at 400∘C in an Ar-based gas flowed at 50 ml/min. We show a reduction of 30% in total scan time compared to conventional step-by-step scanning. The reconstructed Bragg electron density, phase, displacement and strain fields are in excellent agreement with the results obtained from conventional step-by-step scanning. Continuous scanning will allow to minimise sample instability under the beam and will become increasingly important at diffraction-limited storage ring light sources
Continuous scanning for Bragg coherent X-ray imaging
International audienc
Author Correction: Continuous scanning for Bragg coherent X-ray imaging (Scientific Reports, (2020), 10, 1, (12760), 10.1038/s41598-020-69678-5)
This Article contains errors. In Figure 1, the numerical labels for the Log(Intensity) colour scale are in the incorrect position. The correct Figure 1 appears below. (Figure presented.). In Figure 2, three erroneous numerical labels ‘-3.89′, ‘0′ and ‘3.34′ appear above the Strain colour scale. The correct Figure 2 appears below. (Figure presented.)