Design of intense nanoscale stray fields and gradients at magnetic nanorod interfaces

We explore electrodeposited ordered arrays of Fe, Ni, and Co nanorods embedded in anodic alumina membranes as a source of intense magnetic stray field gradients localized at the nanoscale. We perform a multiscale characterization of the stray fields using a combination of experimental methods (magnetooptical Kerr effect and virtual bright field differential phase contrast imaging) and micromagnetic simulations and establish a clear correlation between the stray fields and the magnetic configurations of the nanorods. For uniformly magnetized Fe and Ni wires, the field gradients vary following saturation magnetization of the corresponding metal and the diameter of the wires. In the case of Co nanorods, very localized (similar to 10 nm) and intense (>1 T) stray field sources are associated with the cores of magnetic vortexes. Confinement of that strong field at extremely small dimensions leads to exceptionally high field gradients up to 10(8) T/m. These results demonstrate a clear path to design and fine-tune nanoscale magnetic stray field ordered patterns with a broad applicability in key nanotechnologies, such as nanomedicine, nanobiology, nanoplasmonics, and sensors

Unveiling the mechanisms of the spin Hall effect in Ta

Spin-to-charge current interconversions are widely exploited for the generation and detection of pure spin currents and are key ingredients for future spintronic devices including spin-orbit torques and spin-orbit logic circuits. In case of the spin Hall effect, different mechanisms contribute to the phenomenon and determining the leading contribution is peremptory for achieving the largest conversion efficiencies. Here, we experimentally demonstrate the dominance of the intrinsic mechanism of the spin Hall effect in highly-resistive Ta. We obtain an intrinsic spin Hall conductivity for $\beta$-Ta of -820$\pm$120 ($\hbar$/e) $\Omega^{-1}cm^{-1}$ from spin absorption experiments in a large set of lateral spin valve devices. The predominance of the intrinsic mechanism in Ta allows us to linearly enhance the spin Hall angle by tuning the resistivity of Ta, reaching up to -35$\pm$3%, the largest reported value for a pure metal.Comment: 9 pages and 4 figures + Supplemental Material (2 pages, 3 figures

Synthesis characterisation and photophysical properties of [60]fullerene containing polymers

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Quantification of reagent mixing in liquid flow cells for Liquid Phase-TEM

Liquid-Phase Transmission Electron Microscopy (LP-TEM) offers the opportunity to study nanoscale dynamics of phenomena related to materials and life science in a native liquid environment and in real time. Until now, the opportunity to control/induce such dynamics by changing the chemical environment in the liquid flow cell (LFC) has rarely been exploited due to an incomplete understanding of hydrodynamic properties of LP-TEM flow systems. This manuscript introduces a method for hydrodynamic characterization of LP-TEM flow systems based on monitoring transmitted intensity while flowing a strongly electron scattering contrast agent solution. Key characteristic temporal indicators of solution replacement for various channel geometries were experimentally measured. A numerical physical model of solute transport based on realistic flow channel geometries was successfully implemented and validated against experiments. The model confirmed the impact of flow channel geometry on the importance of convective and diffusive solute transport, deduced by experiment, and could further extend understanding of hydrodynamics in LP-TEM flow systems. We emphasize that our approach can be applied to hydrodynamic characterization of any customized LP-TEM flow system. We foresee the implemented predictive model driving the future design of application-specific LP-TEM flow systems and, when combined with existing chemical reaction models, to a flourishing of the planning and interpretation of experimental observations.This work was supported by the Basque Government (PIBA 2018–34, RIS3 2018222034) and Diputacion Foral de Gipuzkoa (RED2018, RED2019). We acknowledge support by Spanish MINECO under the Maria de Maeztu Units of Excellence Program (MDM-2016–0618). S. M. acknowledges funding from the Basque Ministry of Education in the frame of the “Programa Predoctoral de Formación de Personal Investigador no Doctor” (grant reference: PRE_2019_1_0239).Peer reviewe

Toward sub-second solution exchange dynamics in flow reactors for liquid-phase transmission electron microscopy

Liquid-phase transmission electron microscopy is a burgeoning experimental technique for monitoring nanoscale dynamics in a liquid environment, increasingly employing microfluidic reactors to control the composition of the sample solution. Current challenges comprise fast mass transport dynamics inside the central nanochannel of the liquid cell, typically flow cells, and reliable fixation of the specimen in the limited imaging area. In this work, we present a liquid cell concept – the diffusion cell – that satisfies these seemingly contradictory requirements by providing additional on-chip bypasses to allow high convective transport around the nanochannel in which diffusive transport predominates. Diffusion cell prototypes are developed using numerical mass transport models and fabricated on the basis of existing two-chip setups. Important hydrodynamic parameters, i.e., the total flow resistance, the flow velocity in the imaging area, and the time constants of mixing, are improved by 2-3 orders of magnitude compared to existing setups. The solution replacement dynamics achieved within seconds already match the mixing timescales of many ex-situ scenarios, and further improvements are possible. Diffusion cells can be easily integrated into existing liquid-phase transmission electron microscopy workflows, provide correlation of results with ex-situ experiments, and can create additional research directions addressing fast nanoscale processes.This work was supported by the Basque Government (PIBA 2018-34, RIS3 2018222034, KK-2023/00001) and Diputacion Foral de Gipuzkoa (RED2018, RED2019). We acknowledge support by Spanish MINECO under the Maria de Maeztu Units of Excellence Program (MDM-2016-0618). S.M. acknowledges funding from the Basque Ministry of Education in the frame of the “Programa Predoctoral de Formación de Personal Investigador no Doctor” (grant reference: PRE_2019_1_0239). This work has received funding from the Piedmont region (Italy) through the SATURNO project (POR FESR funding 2014–2020). This study was carried out within the Ministerial Decree no. 1062/2021 and received funding from the FSE REACT-EU - PON Ricerca e Innovazione 2014–2020.Peer reviewe

Conductive Polymer–Inorganic Hybrid Materials through Synergistic Mutual Doping of the Constituents

Polymer-matrix-based inorganic–organic hybrid materials are at the cutting edge of current research for their great promise of merging properties of soft and hard solids in one material. Infiltration of polymers with vapors of reactive metal organics is a pathway for postsynthetic blending of the polymer with inorganic materials. Here, we show that this process is also an excellent method for fabricating conductive hybrid materials. Polyaniline (PANI) was infiltrated with ZnO and the initially insulating polymer was converted to a PANI/ZnO hybrid with conductivities as high as 18.42 S/cm. The conductivity is based on a synergistic effect of the constituting materials, where the inorganic and the polymeric fractions mutually act as dopants for the counterpart. The process temperature is a very important factor for successful infiltration, and the number of applied infiltration cycles allows tuning the level of conductivity of the resulting PANI/ZnO

Spin transport enhancement by controlling the Ag growth in lateral spin valves

The role of the growth conditions onto the spin transport properties of silver (Ag) have been studied by using lateral spin valve structures. By changing the deposition conditions of Ag from polycrystalline to epitaxial growth, we have observed a considerable enhancement of the spin diffusion length, from λAg = 449 ± 30 to 823 ± 59 nm. This enhancement in the spin diffusion length is closely related to the grain size of the Ag channel, which is 19 ± 6 nm for polycrystalline Ag and 41 ± 4 nm for epitaxial Ag. This study shows that diminishing the grain boundary contribution to the spin relaxation mechanism is an effective way to improve the spin diffusion length in metallic nanostructures.This work is supported by the European Union 7th Framework Program under the Marie Curie Actions (256470-ITAMOSCINOM) and the European Research Council (257654- SPINTROS), by the Spanish MINECO (MAT2012-37638 and MAT2012-36844) and by the Basque Government (PI2011-1 and PI2012-47). M. I., E. V., L. F. and O. I. thank the Basque Government for a PhD fellowship (BFI-2011-106, BFI-2010-163, PRE-2013-1- 974 and BFI-2009-284, respectively)