Local magnetization profile and geometry magnetization effects in microwires as determined by magneto-optical Kerr effect

The local magnetization profile along the length in magnetostrictive Fe-based magnetic microwires has been determined by magneto-optical Kerr effect. The study has been performed in microwires with different geometrical dimensions (i.e., diameter and length). The profiles of remanent magnetization and coercivity remain constant at the middle part for all microwires, whereas significant reduction of net magnetization accompanied by significant change of coercivity is observed when approaching their ends. This local region extends just few tens of micrometer for thin (around 1 μm diameter) wires and up to several hundreds of micrometer for thick (around 10 μm diameter) wires. That predicts that critical length to observe bistability goes from 50 μm to nearly 1 mm as diameter increases from 1 to 10 μm. Results are further interpreted considering the local distribution of magnetic charges at the ends which, arising to reduce stray fields, lead in some cases to inverted loops. © 2013 American Institute of Physics.Jingfan Ye acknowledges the support of the German DAAD under the programme “Research Internships in Science and Engineering (RISE-2011).” The work has been supported by the Spanish Ministry of Economy and Competitiviness under projects PLE2009-0057 and MAT2010-20798-C05-01.Peer Reviewe

Epitaxial integration of CoFe₂O₄ thin films on Si (001) surfaces using TiN buffer layers

Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe₂, or ceramic, CoFe₂2O₄, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe₂O₄ [100]/TiN [100]/Si [100]. Mossbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in- plane anisotropy depends on the lattice mismatch between CoFe₂O₂ and TiN, which is larger for CoFe₂O₄ thin films grown on the reactive sputtering process with ceramic targets

Stochastic vs. deterministic magnetic coding in designed cylindrical nanowires for 3D magnetic networks

[EN] Advances in cylindrical nanowires for 3D information technologies profit from intrinsic curvature that introduces significant differences with regards to planar systems. A model is proposed to control the stochastic and deterministic coding of remanent 3D complex vortex configurations in designed multilayered (magnetic/non-magnetic) cylindrical nanowires. This concept, introduced by micromagnetic simulations, is experimentally confirmed by magnetic imaging in FeCo/Cu multilayered nanowires. The control over the random/deterministic vortex states configurations is achieved by a suitable geometrical interface tilting of almost non-interacting FeCo segments with respect to the nanowire axis, together with the relative orientation of the perpendicular magnetic field. The proper design of the segments' geometry (e.g. tilting) in cylindrical nanowires opens multiple opportunities for advanced nanotechnologies in 3D magnetic networks.Spanish Ministry of Science and Innovation under Projects MAT2016-76824-C3-1-R, PID2019-108075RB-C31/ AEI / 10.13039/501100011033 and PGC2018-097789-B-I00 and the Regional Government of Madrid under Project S2018/NMT-4321 NANOMAGCOST-CM. LA and MF acknowledge project RTI2018-095303-B-C53.Peer reviewe

Unveiling the Origin of Multidomain Structures in Compositionally Modulated Cylindrical Magnetic Nanowires

[EN] CoNi/Ni multisegmented cylindrical nanowires were synthesized via an electrochemical route. The wires are 140 nm in diameter, with 1000 nm long Ni segments and CoNi segments between 600 and 1400 nm in length. The magnetic configuration was imaged by XMCD-PEEM in the demagnetized state and at remanence after magnetizing axially and perpendicularly. Ni segments, with cubic crystal symmetry, show an axial magnetic configuration with a small curling component at the surface. In turn, CoNi segments, with hexagonal crystal symmetry and a strong magnetocrystalline anisotropy perpendicular to the nanowires, show a single vortex state in the shorter segments and multivortex or multitransverse magnetic configurations in medium and long segments, respectively. A detailed study by micromagnetic simulations reveals that the magnetic configuration is determined mainly by the coupling between soft Ni and harder CoNi segments. For short CoNi segments, Ni segments are magnetostatically coupled and the chirality of the single vortex formed in CoNi remains the same as that of the curling in neighboring Ni segments. For longer CoNi segments, the remanent state is either the multivortex or multitransverse state depending on whether the previously applied field was parallel or perpendicular to the magnetocrystalline axis. The results point out the relevance of the cylindrical geometry to promote the occurrence of complex magneto-chiral effects and provide key information for the design of cylindrical magnetic nanowires for multiple applications.Support ofSpanish MINECO under Projects MAT2016-76824-C3-1-Rand FIS2016-78591-C3-3-R and the Regional Government of Madrid under Project S2018/NMT-4321 NANOMAGCOST-CM. L.A. and M.F. acknowledge funding through Project RTI2018-095303-B-C53. A.F.R. acknowledges support fromthe Spanish MINECO (Project MAT2015-68772-P). We alsoacknowledge the service from the MiNa Laboratory at IMNand funding from CM (Project SpaceTec, S2013/ICE2822),MINECO (Project CSIC13-4E-1794), and EU (FEDER,FSE)The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.0c03579Peer reviewe

An extraordinary chiral exchange-bias phenomenon: Engineering the sign of the bias field in orthogonal bilayers by a magnetically switchable response mechanism

[EN] Isothermal tuning of both the magnitude and the sign of the bias field has been achieved by exploiting a new phenomenon in a system consisting of two orthogonally coupled films: SmCo (out-of-plane anisotropy)-CoFeB (in-plane anisotropy). This has been achieved by using the large dipolar magnetic field of the SmCo layer resulting in the pinning of one of the branches of the hysteresis loop (either the ascending or the descending branch) at a fixed field value while the second one is modulated along the field axis by varying the orientation of an externally applied magnetic field. This means the possibility of controlling the sign of the bias field in a manner not reported to date. Moreover, modulation of the bias field strength is possible by varying the thickness of a spacer between the SmCo and CoFeB layers. This study shows that the observed phenomena find their origin in the competition between the artificially induced anisotropies in both layers, resulting in a reversible chiral bias effect that allows the selection of the initial sign of the bias field by switching (upwards/downwards) the magnetization in the SmCo film.This research was supported by the Joint German-Spanish Actions Programme (DAAD and Fundación Universidad.es via Ref. 57050243), the Spanish Ministerio de Economía y Competitividad (MINECO) through “SIESPER” (MAT2011-25598) Project, and the Regional Government of Madrid through NANOMAGCOST (P2018/NMT-4321) project. D. S. acknowledges financial support from Xunta de Galicia under the postdoctoral program I2C Plan (Modalidade B) and the Strategic Grouping in Materials (AeMAT; grant No.ED431E2018/08). IMDEA Nanoscience is supported by the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D, MINECO [grant number SEV-2016-0686]Electronic supplementary information (ESI) available. See DOI: 10.1039/c9nr08852

Domain wall propagation and pinning induced by current pulses in cylindrical modulated nanowires

The future developments in 3D magnetic nanotechnology require the control of domain wall dynamics by means of current pulses. While this has been extensively studied in 2D magnetic strips (planar nanowires), few reports on this exist in cylindrical geometry, where Bloch point domain walls are expected to have intriguing properties. Here, we report an investigation on cylindrical magnetic Ni nanowires with geometrical notches. An experimental work based on synchrotron X-ray magnetic circular dichroism (XMCD) combined with photoemission electron microscopy (PEEM) indicates that large current densities induce domain wall nucleation, while smaller currents move domain walls preferably antiparallel to the current direction. In the region where no pinning centers are present, we found a domain wall velocity of about 1 km s. Thermal modelling indicates that large current densities temporarily raise the temperature in the nanowire above the Curie temperature, leading to nucleation of domain walls during the system cooling. Micromagnetic modelling with a spin-torque effect shows that for intermediate current densities, Bloch point domain walls with chirality parallel to the Oersted field propagate antiparallel to the current direction. In other cases, domain walls can be bounced from the notches and/or get pinned outside their positions. We thus found that current is not only responsible for domain wall propagation, but also is a source of pinning due to the Oersted field action.Grants PID2019-108075RB-C31 funded by the Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 and S2018/NMT-4321 NANOMAGCOST-CM funded by the Government of Madrid Region, Spain. We acknowledge the service from the MiNa Laboratory at IMN and the funding from CM (project SpaceTec, S2013/ICE2822), MINECO (project CSIC13-4E-1794), and EU (FEDER, FSE).Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3nr00455

Magnetic properties of spinel-type oxides NiMn2-xMexO4

New materials, based on the well-known spinel compound NiMn2O4, have been synthesized and characterized from the magnetic point of view. The manganese cation was partially substituted in the general formula NiMn2-xMexO4 , by nonmagnetic and magnetic elements, such as Me = Ga, Zn, Ni and Cr (0 x 1). Prior to the determination of their magnetic properties, the non-substituted spinel NiMn2O4 was carefully characterized and studied as a function of the oxygen stoichiometry, based on the influence of the annealing atmosphere and quenching rate. The ferrimagnetic character was observed in all samples, with a paramagnetic-to-ferromagnetic transition temperature Tc stabilized at 110 K, and well defined long-range antiferromagnetic interactions at lower temperatures, which depend on the applied field and the substitute concentrationAuthors from Chile and O.P. thank projects Fondecyt-Chile 1020066, 7020066 and 1050178. Authors from France and Brazil thank project CAPES/COFECUB 416/03. Authors from France thank Région Bretagne for financial supportPeer reviewe

Uncovering Suitable Reference Proteins for Expression Studies in Human Adipose Tissue with Relevance to Obesity

Protein expression studies based on the two major intra-abdominal human fat depots, the subcutaneous and the omental fat, can shed light into the mechanisms involved in obesity and its co-morbidities. Here we address, for the first time, the identification and validation of reference proteins for data standardization, which are essential for accurate comparison of protein levels in expression studies based on fat from obese and non-obese individuals.To uncover adipose tissue proteins equally expressed either in omental and subcutaneous fat depots (study 1) or in omental fat from non-obese and obese individuals (study 2), we have reanalyzed our previously published data based on two-dimensional fluorescence difference gel electrophoresis. Twenty-four proteins (12 in study 1 and 12 in study 2) with similar expression levels in all conditions tested were selected and identified by mass spectrometry. Immunoblotting analysis was used to confirm in adipose tissue the expression pattern of the potential reference proteins and three proteins were validated: PARK7, ENOA and FAA. Western Blot analysis was also used to test customary loading control proteins. ENOA, PARK7 and the customary loading control protein Beta-actin showed steady expression profiles in fat from non-obese and obese individuals, whilst FAA maintained steady expression levels across paired omental and subcutaneous fat samples.ENOA, PARK7 and Beta-actin are proper reference standards in obesity studies based on omental fat, whilst FAA is the best loading control for the comparative analysis of omental and subcutaneous adipose tissues either in obese and non-obese subjects. Neither customary loading control proteins GAPDH and TBB5 nor CALX are adequate standards in differential expression studies on adipose tissue. The use of the proposed reference proteins will facilitate the adequate analysis of proteins differentially expressed in the context of obesity, an aim difficult to achieve before this study

Agenda de investigación: Smart cities y seguridad en Andalucía

Este documento forma parte del proyecto de investigación "Tecnología y control social: Fundamentos de la gobernanza democrática de la seguridad en Andalucía" PAIDI 2020-PI00941La gobernanza de la seguridad en las Smart cities supone un gran reto a nivel de diseño, planificación y gestión. El número de investigadores y grupos de investigación andaluces en esta temática es aún escaso, lo que puede dificultar avanzar de manera significativa y lograr un impacto científico y una competitividad y transferencia internacional de conocimiento. Por eso uno de los objetivos de este proyecto era establecer una agenda de investigación que permitiera identificar hacia la comunidad de investigadores aquellos temas de mayor relevancia con vistas a focalizar los recursos y generar sinergias entre ellos. Además, el futuro próximo de la gestión de la seguridad en las Smart cities requerirá, sin lugar a dudas, un trabajo multidisciplinar que aglutine a investigadores de diferentes campos, así como a la industria y al sector público, lo que debería favorecer que se lancen iniciativas coherentes y se establezcan líneas de investigación sólidas.Proyecto cofinanciado en un 80% por la Unión Europea, en el marco del Programa Operativo FEDER Andalucía 2014-2020 «Crecimiento inteligente: una economía basada en el conocimiento y la innovación». Proyecto financiado por la Consejería de Transformación Económica, Industria, Conocimiento y Universidades. Código P20-00941Informe de 8 páginas fruto de un taller realizado el 6 de marzo de 202

IL-6 serum levels predict severity and response to tocilizumab in COVID-19: An observational study

Background: Patients with coronavirus disaese 2019 (COVID-19) can develop a cytokine release syndrome that eventually leads to acute respiratory distress syndrome requiring invasive mechanical ventilation (IMV). Because IL-6 is a relevant cytokine in acute respiratory distress syndrome, the blockade of its receptor with tocilizumab (TCZ) could reduce mortality and/or morbidity in severe COVID-19. Objective: We sought to determine whether baseline IL-6 serum levels can predict the need for IMV and the response to TCZ. Methods: A retrospective observational study was performed in hospitalized patients diagnosed with COVID-19. Clinical information and laboratory findings, including IL-6 levels, were collected approximately 3 and 9 days after admission to be matched with preadministration and postadministration of TCZ. Multivariable logistic and linear regressions and survival analysis were performed depending on outcomes: need for IMV, evolution of arterial oxygen tension/fraction of inspired oxygen ratio, or mortality. Results: One hundred forty-six patients were studied, predominantly males (66%); median age was 63 years. Forty-four patients (30%) required IMV, and 58 patients (40%) received treatment with TCZ. IL-6 levels greater than 30 pg/mL was the best predictor for IMV (odds ratio, 7.1; P < .001). Early administration of TCZ was associated with improvement in oxygenation (arterial oxygen tension/fraction of inspired oxygen ratio) in patients with high IL-6 (P = .048). Patients with high IL-6 not treated with TCZ showed high mortality (hazard ratio, 4.6; P = .003), as well as those with low IL-6 treated with TCZ (hazard ratio, 3.6; P = .016). No relevant serious adverse events were observed in TCZ-treated patients. Conclusions: Baseline IL-6 greater than 30 pg/mL predicts IMV requirement in patients with COVID-19 and contributes to establish an adequate indication for TCZ administrationThis study was funded by Spanish Ministry of Economy, Industry and Competitiveness (MINECO) and Instituto de Salud Carlos III (grant nos. RD16/0011/0012 and PI18/ 0371 to I.G.A., grant no. PI19/00549 to A.A., and grant no. SAF2017-82886-R to F.S.-M.) and co-funded by the European Regional Development Fund. The study was also funded by ‘‘La Caixa Banking Foundation’’ (grant no. HR17-00016 to F.S.-M.) and ‘‘Fondos Supera COVID19’’ by Banco de Santander and CRUE. None of these sponsors have had any role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publicatio