Search results for "Direct imaging"

Revealing the importance of interfaces for pure spin current transport

2021

Spin transport phenomena underpin an extensive range of spintronic effects. In particular spin transport across interfaces occurs in most device concepts, but is so far poorly understood. As interface properties strongly impact spin transport, one needs to characterize and correlate them to the fabrication method. Here we investigate pure spin current transport across interfaces and connect this with imaging of the interfaces. We study the detection of pure spin currents via the inverse spin Hall effect in Pt and the related spin current absorption by Pt in Py-Cu-Pt lateral spin valves. Depending on the fabrication process, we either find a large (inverse) spin Hall effect signal and low sp…

Mechanism of Néel Order Switching in Antiferromagnetic Thin Films Revealed by Magnetotransport and Direct Imaging.

2019

We probe the current-induced magnetic switching of insulating antiferromagnet/heavy metals systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.

Direct Imaging of Chiral Domain Walls and Néel‐Type Skyrmionium in Ferrimagnetic Alloys

2021

International audience; The evolution of chiral spin structures is studied in ferrimagnet Ta/Ir/Fe/GdFeCo/Pt multilayers as a function of temperature using scanning electron microscopy with polarization analysis (SEMPA). The GdFeCo ferrimagnet exhibits pure right-hand Néel-type domain wall (DW) spin textures over a large temperature range. This indicates the presence of a negative Dzyaloshinskii-Moriya interaction (DMI) that can originate from both the top Fe/Pt and the Co/Pt interfaces. From measurements of the DW width, as well as complementary magnetic characterization, the exchange stiffness as a function of temperature is ascertained. The exchange stiffness is surprisingly mostly const…

Direct imaging of current-induced antiferromagnetic switching revealing a pure thermomagnetoelastic switching mechanism in NiO

2021

We unambiguously identify the origin of the current-induced magnetic switching of insulating antiferromagnet/heavy metal bilayers. Previously, different reorientations of the Neel order for the same current direction were reported for different device geometries and different switching mechanisms were proposed. Here, we combine concurrent electrical readout and optical imaging of the switching of antiferromagnetic domains with simulations of the current-induced temperature and strain gradients. By comparing the switching in specially engineered NiO/Pt device and pulsing geometries, we can rule out spin-orbit torque based mechanisms and identify a thermomagnetoelastic mechanism to dominate t…

Imaging Trapped Ion Structures via Fluorescence Cross-Correlation Detection

2021

Cross-correlation signals are recorded from fluorescence photons scattered in free space off a trapped ion structure. The analysis of the signal allows for unambiguously revealing the spatial frequency, thus the distance, as well as the spatial alignment of the ions. For the case of two ions we obtain from the cross-correlations a spatial frequency ${f}_{\text{spatial}}=1490\ifmmode\pm\else\textpm\fi{}{2}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{8}_{\mathrm{syst}}\text{ }\text{ }{\mathrm{rad}}^{\ensuremath{-}1}$, where the statistical uncertainty improves with the integrated number of correlation events as ${N}^{\ensuremath{-}0.51\ifmmode\pm\else\textpm\fi{}0.06}$. We independently deter…

SOLAR DYNAMICS OBSERVATORY DISCOVERS THIN HIGH TEMPERATURE STRANDS IN CORONAL ACTIVE REGIONS

2011

One scenario proposed to explain the million degrees solar corona is a finely-stranded corona where each strand is heated by a rapid pulse. However, such fine structure has neither been resolved through direct imaging observations nor conclusively shown through indirect observations of extended superhot plasma. Recently it has been shown that the observed difference in appearance of cool and warm coronal loops (~1 MK, ~2-3 MK, respectively) -- warm loops appearing "fuzzier" than cool loops -- can be explained by models of loops composed of subarcsecond strands, which are impulsively heated up to ~10 MK. That work predicts that images of hot coronal loops (>~6 MK) should again show fine s…

Caffeine as a Gelator

2016

Caffeine (a stimulant) and ethanol (a depressant) may have opposite effects in our body, but under in vitro conditions they can “gel” together. Caffeine, being one of the widely used stimulants, continued to surprise the scientific community with its unprecedented biological, medicinal and physicochemical properties. Here, we disclose the supramolecular self-assembly of anhydrous caffeine in a series of alcoholic and aromatic solvents, rendering a highly entangled microcrystalline network facilitating the encapsulation of the solvents as illustrated using direct imaging, microscopy analysis and NMR studies. Peer reviewed

1986

MRI of Pulmonary Ventilation

2008

Gas imaging has opened the new field of direct imaging of pulmonary ventilation by MRI. The use of hyperpolarised 3He gas for MRI of the lung has been pioneered by a number of groups worldwide. Due to the enormous progress in the fields of hyperpolarisation technology, administration of hyperpolarised 3He, MR hardware, and MR pulse sequences significant progress has been made and the translation into the clinical arena has been accomplished. This chapter gives an overview of the technical methods for HP 3He MRI for human lung imaging, focusing on gas polarisation methods, background physics, MRI hardware considerations, MRI pulse sequence considerations, safety considerations for imaging in…