Corriente crítica y mecanismos de disipación en películas y superredes de superconductores de alta Tc (relación con la microestructura y propiedades de anisotropía)

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de Materiales, leída el 13-12-1995En esta tesis hemos empleado distintas técnicas de medida de corriente critica para el estudio de monocristales superconductores de baja temperatura: liti2o4 y el superconductor orgánico k(et)2cu(ncs)2, así como de películas delgadas de superconductores de alta tc. Estas últimas fueron crecidas por pulverización catódica tipo magnetrón, tanto láminas simples de euba2cu3o7 como superredes superconductor/aislante de dos sistemas: euba2cu3o7/prba2cu3o7 y euba2cu3o7/srtio3, con orientaciones eje-c y eje-a. Se ha estudiado la corriente crítica y las propiedades de transporte en el estado mixto de las películas eje-a simples para comprender mejor el papel jugado por los distintos mecanismos de disipación relacionándolo con su microestructura. Asimismo, hemos estudiado las propiedades de anisotropía de estas láminas y la influencia de la estructura de multicapa cuando se halla bien paralela o bien perpendicular a los planos de cuo2.Depto. de Física de MaterialesFac. de Ciencias FísicasTRUEpu

Cycloidal Domains in the Magnetization Reversal Process of Ni80Fe20/Nd16Co84/Gd12Co88 Trilayers

The magnetization reversal of each individual layer in magnetic trilayers ( permalloy / Nd Co / Gd Co ) 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 Ni Fe layer, as estimated from the stability of cycloid domains in the sample

Enhancement of synchronized vortex lattice motion in hybrid magnetic/amorphous superconducting nanostructures

et al.Superconducting a-Mo3Si and Nb films have been grown on arrays of Ni nanodots. We have studied the vortex lattice dynamics close to critical temperatures. Different vortex lattice configurations are obtained with the same array unit cell. These different vortex lattices occur at matching conditions between the vortex lattice and the array unit cell. The interplay between the random intrinsic pinning of the superconducting films and the periodic pinning of the array govern the vortex lattice configurations. Different vortex lattice configurations and enhancement of synchronized vortex lattice motion are obtained by increasing the periodic pinning strength and decreasing the random pinning strength.This work was supported by the Spanish Ministerio Ciencia e Innovacion, Grant Nos. NAN2004-09087 and FIS2005-07392, Consolider Grant Nos. CSD2007-00010 and FIS2008-06249 (Grupo Consolidado), CAM Grant No. S-0505/ESP/0337, and Fondo Social Europeo and Junta de Comunidades de Castilla-La Mancha Grant No. PAI08-0067-2673. A.A. wants to thank PCTI BP06-109.Peer reviewe

Magnetization processes in rectangular versus rhombic planar superlattices of magnetic bars

4 páginas, 5 figuras.-- PACS number(s): 75.60.Ej, 75.60.Jk, 75.70.Kw, 75.75.Cd.-- et al.Rectangular and rhombic patterned superlattices of magnetic bar elements have been experimentally studied and theoretically modeled in order to analyze the role of the array geometry in their magnetization reversal and coercivity. The results show that a dominating part of the coercive field (≈250 Oe) is due to the reversal processes within a single bar element (independent of the array geometry) which is well described by the standard micromagnetic calculation. Otherwise, a smaller (≈60 Oe) but significant difference between the magnetization loops in the two geometries is related to the magnetostatic coupling effects between the bars and it is reasonably accounted for with a simple model of Coulomb-like interaction between terminal magnetic charges. The possibility to use this geometry effect to control the performance of artificial magnetic media is discussed.The support of this work by Spanish and Portuguese Grants Nos. HP2008-0032, FIS2008-6249, PCTI IB08-106, FCT SFRH/BPD/72329/2010 (J.M.T.) is gratefully acknowledged. G.N.K. acknowledges support from Portuguese FCT through the “Ciencia 2007” program. Work in Ukraine was supported by STCU through the Project No. 5210.Peer reviewe

Magnetic properties of amorphous Co0.74Si0.26/Si multilayers with different numbers of periods

Two sets of [Co0.74Si0.26(5nm)∕Si(s)]n amorphous films were prepared by magnetron sputtering: one in the form of multilayers with the Si spacer thickness s fixed at 3nm, and the number n of periods varying from 1 to 10 and the other with only two periods and s varying from 3to24nm (trilayers). In both sets, the Co0.74Si0.26 layer thickness t was fixed at 5nm. All the samples except the one with s=24nm manifest antiferromagnetic coupling. Their magnetic properties at room temperature were probed using the magnetooptical transverse Kerr effect (MOTKE) and ferromagnetic resonance (FMR). The relative increase in the saturation magnetization Ms (for trilayers, relative to a structure with s=24nm; for multilayers, relative to the single-layer structure) determined from the FMR measurements was compared with the exchange coupling strength HAFJ obtained from the MOTKE studies. The dependences of HAFJ and Ms on n and s were found to be very similar to each other. Possible mechanisms of this similarity are discussed.This work was supported by MICINN of Spain (grants Nos. HP2008-0032, NAN2004-09087 and FIS2008-06249) and CRUP of Portugal (grant No. E41/09) in the framework of the Spanish-Portuguese Integrated Action. G.N.K acknowledges support from FCT of Portugal through the “Ciencia 2007” program. C.Q. acknowledges support from the Spanish Government and European Social Fund under the “Ramón y Cajal” program.Peer reviewe

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

CIBERER : Spanish national network for research on rare diseases: A highly productive collaborative initiative

Altres ajuts: Instituto de Salud Carlos III (ISCIII); Ministerio de Ciencia e Innovación.CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research

Corriente crítica y mecanismos de disipación en películas y superredes de superconductores de alta Tc (relación con la microestructura y propiedades de anisotropía)

En esta tesis hemos empleado distintas técnicas de medida de corriente critica para el estudio de monocristales superconductores de baja temperatura: liti2o4 y el superconductor orgánico k(et)2cu(ncs)2, así como de películas delgadas de superconductores de alta tc. Estas últimas fueron crecidas por pulverización catódica tipo magnetrón, tanto láminas simples de euba2cu3o7 como superredes superconductor/aislante de dos sistemas: euba2cu3o7/prba2cu3o7 y euba2cu3o7/srtio3, con orientaciones eje-c y eje-a. Se ha estudiado la corriente crítica y las propiedades de transporte en el estado mixto de las películas eje-a simples para comprender mejor el papel jugado por los distintos mecanismos de disipación relacionándolo con su microestructura. Asimismo, hemos estudiado las propiedades de anisotropía de estas láminas y la influencia de la estructura de multicapa cuando se halla bien paralela o bien perpendicular a los planos de cuo2