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 $La_{0.7}Sr_{0.3}MnO_{3}$ 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 $MnO_{6}$ 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 $Mn-O$ average bond distance and the increase of $Mn-Mn$ length matching with the enlargement of the cell parameter. From these results we conclude that there is no significant change in the $Mn-O-Mn$ 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 $\alpha$ 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

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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.)