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L'article est en accès libre. Je n'arrive pas à ouvrir la fenêtre concernant l'embargo pour pouvoir le mettre en accès libre immédiat. Merci, Eric ; International audience ; In this article, we show that the chaos and urgency induced by the coronavirus disease 2019 (COVID-19) pandemic has led to massive fossil fuel-derived plastic production, largely ignoring recent environmental policies. Solutions for a sustainable and circular economy require radical innovations, consumer education and most importantly political willingness.

L'article est en accès libre. Je n'arrive pas à ouvrir la fenêtre concernant l'embargo pour pouvoir le mettre en accès libre immédiat. Merci, Eric ; International audience ; In this article, we show that the chaos and urgency induced by the coronavirus disease 2019 (COVID-19) pandemic has led to massive fossil fuel-derived plastic production, largely ignoring recent environmental policies. Solutions for a sustainable and circular economy require radical innovations, consumer education and most importantly political willingness.

L'article est en accès libre. Je n'arrive pas à ouvrir la fenêtre concernant l'embargo pour pouvoir le mettre en accès libre immédiat. Merci, Eric ; International audience ; In this article, we show that the chaos and urgency induced by the coronavirus disease 2019 (COVID-19) pandemic has led to massive fossil fuel-derived plastic production, largely ignoring recent environmental policies. Solutions for a sustainable and circular economy require radical innovations, consumer education and most importantly political willingness.

Energy-dependent full field transmission soft X-ray microscopy (TXM) is able to give a full picture at the nanometer scale of the chemical state and spatial distribution of oxygen and other elements relevant for battery materials, providing pixel-by-pixel absorption spectrum. We show different methods to localize chemical inhomogeneities in Li1.2Mn0.56Ni0.16Co0.08O2 particles with and without VOx coating extracted from electrodes at different states of charge. Considering the 3d(Mn,Ni)-2p(O) hybridization, it has been possible to discriminate the chemical state of Mn and Ni in addition to the one of O. Different oxidation states correspond to specific features in the O-K spectra. To localize sample regions with specific compositions we apply two different methods. In the first, the pixel-by-pixel ratios of images collected at different key energies clearly highlight local inhomogeneities. In the second, introduced here for the first time, we directly correlate corresponding pixels of the two images on a xy scatter plot that we call phase map, where we can visualize the distributions as function of thickness as well as absorption artifacts. We can select groups of pixels, and then map regions with similar spectral features. Core-shell distributions of composition are clearly shown in these samples. The coating appears in part to frustrate some of the usual chemical evolution. In addition, we could directly observe several further aspects, such as: distribution of conducting carbon; inhomogeneous state of charge within the electrode; molecular oxygen profiles within a particle. The latter suggests a surface loss with respect to the bulk but an accumulation layer at intermediate depth that could be assigned to retained O2. ; This research was funded by Spanish Government, through the "Severo Ochoa" Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S), and the projects MAT2017-91404-EXP, RTI2018-096273-B-I00 and RTI2018-097753-B-I00 with FEDER cofunding. D.T. participates in the FLOWBAT 2021 platforms promoted by the Spanish National Research Council (CSIC). The HIU authors acknowledge the basic funding from the Helmholtz Association. ; Peer reviewed

Resumen del trabajo presentado al American Physical Society March Meeting, celebrado on-line del 15 al 19 de marzo de 2021. ; Work supported by Spanish MINECO (Grants FIS2016-76058 (AEI/FEDER, EU) and PID2019-104604RB/AEI/10.13039/501100011033) and European Union's Horizon 2020 Marie Sklodowska-Curie Grant ref. H2020-MSCA-IF-2016-746958. ; Peer reviewed

The knowledge of how magnetization looks inside a ferromagnet is often hindered by the limitations of the available experimental methods which are sensitive only to the surface regions or limited in spatial resolution. Here we report a vector tomographic reconstruction based on soft X-ray transmission microscopy and magnetic dichroism data, which has allowed visualizing the three-dimensional magnetization in a ferromagnetic thin film heterostructure. Different non-trivial topological textures have been resolved and the determination of their topological charge has allowed us to identify a Bloch point and a meron-like texture. Our method relies only on experimental data and might be of wide application and interest in 3D nanomagnetism. ; Alba light source is funded by the Ministry of Research and Innovation of Spain and by the Generalitat de Catalunya and by European FEDER funds. This project has been supported by Spanish MINECO under grant FIS2016-76058 (AEI/FEDER, EU) and grant PID2019-104604RB/AEI/10.13039/501100011033. A.H.-R. and S.MV. acknowledge the support from European Union's Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant ref. H2020-MSCA-IF-2016-746958. ; Peer reviewed

The magnetization reversal of each individual layer in magnetic trilayers (permalloy/NdCo/GdCo) is investigated in detail with x-ray microscopy and micromagnetic calculations. Two sequential inversion mechanisms are identified. First, magnetic vortex-antivortex pairs move along the field direction while inverting the magnetization of magnetic stripes until they are pinned by defects. The vortex-antivortex displacements are reversible within a field interval which allows their controlled motion. Second, as the reversed magnetic field increases, cycloidal domains appear in the permalloy layer as a consequence of the dissociation of vortex-antivortex pairs due to pinning. The field range where magnetic vortices and antivortices are effectively guided by the stripe pattern is of the order of tens of mT for the NiFe layer, as estimated from the stability of cycloid domains in the sample. ; Work supported by Spanish MINECO [Grants No. FIS 2013-45469 and No. FIS2016-76058 (AEI/FEDER,EU)] and by FICYT-Asturias (Grant No. FC-GRUPIN14-040). We thank J. Avila (Alba staff) for assistance in the pulsed magnetic field set up. We thank Unidad de Medidas magnéticas y RMN de Sólidos de los Servicios Cientifico Técnicos of Universidad de Oviedo for the VSM characterization. A.H.-R. acknowledges the support from European Union's Horizon 2020 research and innovation programme under Marie Skłodowska-Curie Grant No. H2020-MSCAIF-2016-746958. ; Peer Reviewed

The development of magnetic nanostructures for applications in spintronics requires methods capable of visualizing their magnetization. Soft X-ray magnetic imaging combined with circular magnetic dichroism allows nanostructures up to 100–300 nm in thickness to be probed with resolutions of 20–40 nm. Here a new iterative tomographic reconstruction method to extract the three-dimensional magnetization configuration from tomographic projections is presented. The vector field is reconstructed by using a modified algebraic reconstruction approach based on solving a set of linear equations in an iterative manner. The application of this method is illustrated with two examples (magnetic nano-disc and micro-square heterostructure) along with comparison of error in reconstructions, and convergence of the algorithm. ; The following funding is acknowledged: Spanish MINECO (grant No. FIS2013-45469; grant No. FIS2016-76058 (AEI/FEDER, EU); contract No. FIS2016-76058 (AEI/FEDER, EU) to AHR); FICYT-Asturias (grant No. FC-GRUPIN14-040); US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (contract No. DE-AC02-06CH11357 to DG); US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division (contract to CP). AHR acknowledges support from European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Action (reference H2020-MSCA-IF-2016-746958). ; Peer Reviewed

This project has been supported by Spanish MINECO under grant FIS2016-76058 (AEI/FEDER, EU) and grant PID2019-104604RB/AEI/10.13039/501100011033. A.H.-R. and S.MV. acknowledge the support from European Union's Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant ref. H2020-MSCA-IF-2016-746958.

Chirality plays a major role in nature, from particle physics to DNA, and its control is much sought-after due to the scientific and technological opportunities it unlocks. For magnetic materials, chiral interactions between spins promote the formation of sophisticated swirling magnetic states such as skyrmions, with rich topological properties and great potential for future technologies. Currently, chiral magnetism requires either a restricted group of natural materials or synthetic thin-film systems that exploit interfacial effects. Here, using state-of-the-art nanofabrication and magnetic X-ray microscopy, we demonstrate the imprinting of complex chiral spin states via three-dimensional geometric effects at the nanoscale. By balancing dipolar and exchange interactions in an artificial ferromagnetic double-helix nanostructure, we create magnetic domains and domain walls with a well-defined spin chirality, determined solely by the chiral geometry. We further demonstrate the ability to create confined 3D spin textures and topological defects by locally interfacing geometries of opposite chirality. The ability to create chiral spin textures via 3D nanopatterning alone enables exquisite control over the properties and location of complex topological magnetic states, of great importance for the development of future metamaterials and devices in which chirality provides enhanced functionality. ; This work was funded by EPSRC Early Career Fellowship EP/M008517/1, the Winton Program for the Physics of Sustainability, and the EU CELINA COST action. D.S.-H. acknowledges a Girton College Pfeiffer scholarship and support from the EPSRC CDT in Nanoscience and Nanotechnology. A.H.-R. and S.M.V. acknowledge funding from the EU Horizon 2020 program through Marie Skłodowska-Curie Action H2020-MSCA-IF-2016-74695. C.D. acknowledges funding from Leverhulme Trust (ECF-2018-016), Isaac Newton Trust (18-08), and a L'Oréal-UNESCO UK and Ireland Fellowship for Women in Science 2019. Funding by the Spanish Ministry of Science is acknowledged, grants MAT2017-82970-C2-1-R, MAT2017-82970-C2-2-R and MAT2018-102627-T, and by Aragon Government (Construyendo Europa desde Aragón), grant E13_20R including European Social Fund. J.P.-N. acknowledges MINECO funding BES-2015-072950. S.M.V. appreciates support from EPSRC EP/M024423/1. P.F. was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, Contract No. DE-AC02-05-CH11231 (NEMM program MSMAG). These experiments were performed at MISTRAL beamline at ALBA Synchrotron with the collaboration of ALBA staff and CALIPSOplus (Grant 730872) funding. ; Peer reviewed

(.) Funding by the Spanish Ministry of Science is acknowledged, grants MAT2017-82970-C2-1-R, MAT2017-82970-C2-2-R and MAT2018-102627-T, and by Aragón Government (Construyendo Europa desde Aragón), grant E13_20R including European Social Fund. J.P.-N. acknowledges MINECO funding BES-2015-072950. (.)