An effective method to probe local magnetostatic properties in a nanometric FePd antidot array

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A simple method to quantitatively characterize the local magnetic behaviour of a patterned nanostructure, like a ferromagnetic thin film of antidot arrays, is proposed. The first-order reversal curve (FORC) analysis, coupled with simulations using physically meaningful hysterons, allows us to obtain a quantitative and physically related description of the interaction field and each magnetization reversal process. The hysterons system is built from previously known hypotheses on the magnetic behaviour of the sample. This method was successfully applied to a highly hexagonal ordered FePd antidot array with nanometric dimensions. We achieved a complete characterization of the two different magnetization reversal mechanisms in function of the in-plane applied field angle. For a narrow range of high fields, the magnetization initiates rotating reversibly around the pores, while at lower fields, domain walls are nucleated and propagated. This in-plane magnetization reversal mechanism, partly reversible and partly irreversible, is the only angularly dependent one. While going away from the easy axis, its reversible proportion increases, as well as its switching field distribution. Finally, the results indicate that the high surface roughness between adjacent holes of the antidot thin film induces a parallel interaction field. The proposed method demonstrates its ability also to be applied to characterizing patterned nanostructures with rather complex magnetization reversal processes.13Fonds Quebecois de Recherche sur la Nature et les Technologies (FQRNT), CanadaFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Spanish Government MICINNEU [MAT2009-13108-C02-01, MAT2010-20798-C05-04]FICYT [FC-09-IB09-131]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)John Simon Guggenheim Memorial FoundationFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)EU [MAT2009-13108-C02-01, MAT2010-20798-C05-04]FICYT [FC-09-IB09-131

Tailoring of magnetocaloric response in nanostructured materials: Role of anisotropy

The magnetocaloric response of an ensemble of oriented uniaxial magnetic objects, perpendicularly magnetized to their easy axes, for temperatures close to the blocking temperature is calculated with the aim of demonstrating that the control of the sample's microstructure makes up an effective way to tailor its magnetocaloric response. Coexisting positive and negative magnetocaloric effect (MCE) is found for a model material with a single magnetic phase transition. Both MCE regimes are controlled by the magnitude of the applied magnetic field. As a proof of concept, experimental results for arrays of self-assembled ferromagnetic nanowires embedded into highly ordered nanoporous anodic alumina templates are shown, suggesting the validity of the numerical calculations.771

Magnetization Reversal in Radially Distributed Nanowire Arrays

© 2018 American Chemical Society. The magnetic properties of radially oriented Co, Ni, and CoNi alloy nanowires synthesized by pulsed electrodeposition into porous alumina structures are measured and compared with those of similar nanowires grown in a planar geometry. The alloy composition affects the anisotropy axis direction, which is determined by the balance between the magnetocrystalline and shape anisotropies, lying transverse to the nanowires for Co samples and along the nanowire axis for Ni. Monte Carlo simulations were performed to model the magnetic hysteresis of the radially oriented and planar geometry nanowires using an approach based on the conical distribution of anisotropies. The model provides an excellent fit compared with experimental hysteresis loops

Template-Assisted CoPd Nanowire Arrays: Magnetic Properties and FORC Analysis

Highly hexagonally ordered CoPd alloy nanowire arrays were synthesized through electrochemical deposition techniques into the nanopores of anodic alumina membranes used as templates. Two different electrolytes were used for this purpose, one with pH = 4.1 and the other with pH = 7. Under applying different electrodeposition parameters and by adjusting both, the current density and the electrolyte composition, it could be possible make to vary the composition of CoPd alloy nanowires in a wide range. Their composition and morphology were investigated by SEM and EDX. The magnetic properties of the nanowires array have been measured with a VSM as a function of the temperature, ranging from RT down to 50 K, for different CoPd alloy nanowires composition. Also, the temperature influence on the reversible-irreversible magnetization processes related with the magnetization reversal of the CoPd nanowires array has been analyzed by first order reversal curve (FORC) method.12647364743FEDERSpanish MICINNFICyT [MAT2009-13108-C02-01, MAT2010-20798-C05-04, FC09-IB09-131, FC-10-COF10-04, BP07-075, BP10-035]FICyT [MAT2009-13108-C02-01, MAT2010-20798-C05-04, FC09-IB09-131, FC-10-COF10-04, BP07-075, BP10-035

Dengue virus sero-cross-reactivity drives antibody-dependent enhancement of infection with zika virus

Zika virus (ZIKV) was discovered in 1947 and was thought to lead to relatively mild disease. The recent explosive outbreak of ZIKV in South America has led to widespread concern, with reports of neurological sequelae ranging from Guillain Barré syndrome to microcephaly. ZIKV infection has occurred in areas previously exposed to dengue virus (DENV), a flavivirus closely related to ZIKV. Here we investigated the serological cross-reaction between the two viruses. Plasma immune to DENV showed substantial cross-reaction to ZIKV and was able to drive antibody-dependent enhancement (ADE) of ZIKV infection. Using a panel of human monoclonal antibodies (mAbs) to DENV, we showed that most antibodies that reacted to DENV envelope protein also reacted to ZIKV. Antibodies to linear epitopes, including the immunodominant fusion-loop epitope, were able to bind ZIKV but were unable to neutralize the virus and instead promoted ADE. Our data indicate that immunity to DENV might drive greater ZIKV replication and have clear implications for disease pathogenesis and future vaccine programs for ZIKV and DENV