scholarly journals Revealing 3D magnetization of thin films with soft X-ray tomography: magnetic singularities and topological charges

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Hierro-Rodriguez ◽  
C. Quirós ◽  
A. Sorrentino ◽  
L. M. Alvarez-Prado ◽  
J. I. Martín ◽  
...  
Keyword(s):  
Thin Film ◽  
Topological Charge ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Experimental Methods ◽  
Transmission Microscopy ◽  
X Ray ◽  
Magnetic Dichroism ◽  
Topological Charges

AbstractThe knowledge of how magnetization looks inside a ferromagnet is often hindered by the limitations of the available experimental methods which are sensitive only to the surface regions or limited in spatial resolution. Here we report a vector tomographic reconstruction based on soft X-ray transmission microscopy and magnetic dichroism data, which has allowed visualizing the three-dimensional magnetization in a ferromagnetic thin film heterostructure. Different non-trivial topological textures have been resolved and the determination of their topological charge has allowed us to identify a Bloch point and a meron-like texture. Our method relies only on experimental data and might be of wide application and interest in 3D nanomagnetism.

scholarly journals 3D reconstruction of magnetization from dichroic soft X-ray transmission tomography

2018 ◽  
Vol 25 (4) ◽  
pp. 1144-1152 ◽  
Author(s):  
Aurelio Hierro-Rodriguez ◽  
Doga Gürsoy ◽  
Charudatta Phatak ◽  
Carlos Quirós ◽  
Andrea Sorrentino ◽  
...  
Keyword(s):  
Vector Field ◽  
Tomographic Reconstruction ◽  
Linear Equations ◽  
Three Dimensional ◽  
Magnetic Nanostructures ◽  
Reconstruction Method ◽  
Transmission Tomography ◽  
X Ray ◽  
Magnetic Imaging ◽  
Magnetic Dichroism

The development of magnetic nanostructures for applications in spintronics requires methods capable of visualizing their magnetization. Soft X-ray magnetic imaging combined with circular magnetic dichroism allows nanostructures up to 100–300 nm in thickness to be probed with resolutions of 20–40 nm. Here a new iterative tomographic reconstruction method to extract the three-dimensional magnetization configuration from tomographic projections is presented. The vector field is reconstructed by using a modified algebraic reconstruction approach based on solving a set of linear equations in an iterative manner. The application of this method is illustrated with two examples (magnetic nano-disc and micro-square heterostructure) along with comparison of error in reconstructions, and convergence of the algorithm.

Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 264-265
Author(s):  
D. R. Liu ◽  
S. S. Shinozaki ◽  
R. J. Baird
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Compound Semiconductors ◽  
Energy Dispersive Analysis ◽  
X Ray ◽  
Metastable Alloys ◽  
Lower Voltage

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.

Problems in Thin-Film X-ray Quantification

1990 ◽  
Vol 48 (2) ◽  
pp. 458-459
Author(s):  
J N Chapman ◽  
W A P Nicholson
Keyword(s):  
Thin Film ◽  
Specimen Thickness ◽  
X Rays ◽  
Characteristic Peak ◽  
Local Composition ◽  
X Ray ◽  
Measured Ratio ◽  
Path Lengths ◽  
Composition Changes

Energy dispersive x-ray microanalysis (EDX) is widely used for the quantitative determination of local composition in thin film specimens. Extraction of quantitative data is usually accomplished by relating the ratio of the number of atoms of two species A and B in the volume excited by the electron beam (nA/nB) to the corresponding ratio of detected characteristic photons (NA/NB) through the use of a k-factor. This leads to an expression of the form nA/nB = kAB NA/NB where kAB is a measure of the relative efficiency with which x-rays are generated and detected from the two species.Errors in thin film x-ray quantification can arise from uncertainties in both NA/NB and kAB. In addition to the inevitable statistical errors, particularly severe problems arise in accurately determining the former if (i) mass loss occurs during spectrum acquisition so that the composition changes as irradiation proceeds, (ii) the characteristic peak from one of the minority components of interest is overlapped by the much larger peak from a majority component, (iii) the measured ratio varies significantly with specimen thickness as a result of electron channeling, or (iv) varying absorption corrections are required due to photons generated at different points having to traverse different path lengths through specimens of irregular and unknown topography on their way to the detector.

scholarly journals Determination of the Three-dimensional Structure of Dislocations by Synchrotron White X-ray Topography Combined with a Topo-tomographic Technique

Materia Japan ◽  
2007 ◽  
Vol 46 (12) ◽  
pp. 823-823
Author(s):  
Seiji Kawado ◽  
Toshinori Taishi ◽  
Satoshi Iida ◽  
Yoshifumi Suzuki ◽  
Yoshinori Chikaura ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Dimensional Structure ◽  
X Ray ◽  
Three Dimensional Structure ◽  
Tomographic Technique

scholarly journals Three-dimensional imaging of hold baggage for airport security

2014 ◽  
Vol XL-5 ◽  
pp. 331-336
Author(s):  
S. Kolokytha ◽  
R. Speller ◽  
S. Robson
Keyword(s):  
3D Imaging ◽  
Imaging System ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Handling Time ◽  
Cost Effective ◽  
Airport Security ◽  
X Ray ◽  
Common System ◽  
Close Range

This study describes a cost-effective check-in baggage screening system, based on "on-belt tomosynthesis" (ObT) and close-range photogrammetry, that is designed to address the limitations of the most common system used, conventional projection radiography. The latter's limitations can lead to loss of information and an increase in baggage handling time, as baggage is manually searched or screened with more advanced systems. This project proposes a system that overcomes such limitations creating a cost-effective automated pseudo-3D imaging system, by combining x-ray and optical imaging to form digital tomograms. Tomographic reconstruction requires a knowledge of the change in geometry between multiple x-ray views of a common object. This is uniquely achieved using a close range photogrammetric system based on a small network of web-cameras. This paper presents the recent developments of the ObT system and describes recent findings of the photogrammetric system implementation. Based on these positive results, future work on the advancement of the ObT system as a cost-effective pseudo-3D imaging of hold baggage for airport security is proposed.

X-ray topographic determination of the granular structure in a graphite mosaic crystal: a three-dimensional reconstruction

2000 ◽  
Vol 33 (4) ◽  
pp. 1023-1030 ◽  
Author(s):  
M. Ohler ◽  
M. Sanchez del Rio ◽  
A. Tuffanelli ◽  
M. Gambaccini ◽  
A. Taibi ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Pyrolytic Graphite ◽  
Three Dimensional ◽  
X Ray ◽  
Dimensional Reconstruction ◽  
Mosaic Crystals ◽  
Spatial Locations ◽  
Crystalline Domains

Section topographs recorded at different spatial locations and at different rocking angles of a highly oriented pyrolytic graphite (HOPG) crystal allow three-dimensional maps of the local angular-dependent scattering power to be obtained. This is performed with a direct reconstruction from the intensity distribution on such topographs. The maps allow the extraction of information on local structural parameters such as size, form and internal mosaic spread of crystalline domains. This data analysis leads to a new method for the characterization of mosaic crystals. Perspectives and limits of applicability of this method are discussed.

Structure determination of a partially ordered layered silicate material with an NMR crystallography approach

2017 ◽  
Vol 73 (3) ◽  
pp. 184-190 ◽  
Author(s):  
Darren Henry Brouwer ◽  
Sylvian Cadars ◽  
Kathryn Hotke ◽  
Jared Van Huizen ◽  
Nicholas Van Huizen
Keyword(s):  
Nmr Spectroscopy ◽  
Structure Determination ◽  
Three Dimensional ◽  
Layered Silicate ◽  
Silicate Layer ◽  
Silicate Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nmr Crystallography

Structure determination of layered materials can present challenges for conventional diffraction methods due to the fact that such materials often lack full three-dimensional periodicity since adjacent layers may not stack in an orderly and regular fashion. In such cases, NMR crystallography strategies involving a combination of solid-state NMR spectroscopy, powder X-ray diffraction, and computational chemistry methods can often reveal structural details that cannot be acquired from diffraction alone. We present here the structure determination of a surfactant-templated layered silicate material that lacks full three-dimensional crystallinity using such an NMR crystallography approach. Through a combination of powder X-ray diffraction and advanced 29Si solid-state NMR spectroscopy, it is revealed that the structure of the silicate layer of this layered silicate material templated with cetyltrimethylammonium surfactant cations is isostructural with the silicate layer of a previously reported material referred to as ilerite, octosilicate, or RUB-18. High-field 1H NMR spectroscopy reveals differences between the materials in terms of the ordering of silanol groups on the surfaces of the layers, as well as the contents of the inter-layer space.

Polarity determination of a GaN thin film on sapphire (0001) with x-ray standing waves

1998 ◽  
Vol 84 (3) ◽  
pp. 1703-1705 ◽  
Author(s):  
A. Kazimirov ◽  
G. Scherb ◽  
J. Zegenhagen ◽  
T.-L. Lee ◽  
M. J. Bedzyk ◽  
...  
Keyword(s):  
Thin Film ◽  
Standing Waves ◽  
X Ray ◽  
Polarity Determination

scholarly journals Role of Computational Methods in Going beyond X-ray Crystallography to Explore Protein Structure and Dynamics

2018 ◽  
Vol 19 (11) ◽  
pp. 3401 ◽  
Author(s):  
Ashutosh Srivastava ◽  
Tetsuro Nagai ◽  
Arpita Srivastava ◽  
Osamu Miyashita ◽  
Florence Tama
Keyword(s):  
Protein Dynamics ◽  
Computational Methods ◽  
Protein Structures ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
X Ray ◽  
X Ray Crystallography ◽  
Insight Into

Protein structural biology came a long way since the determination of the first three-dimensional structure of myoglobin about six decades ago. Across this period, X-ray crystallography was the most important experimental method for gaining atomic-resolution insight into protein structures. However, as the role of dynamics gained importance in the function of proteins, the limitations of X-ray crystallography in not being able to capture dynamics came to the forefront. Computational methods proved to be immensely successful in understanding protein dynamics in solution, and they continue to improve in terms of both the scale and the types of systems that can be studied. In this review, we briefly discuss the limitations of X-ray crystallography in studying protein dynamics, and then provide an overview of different computational methods that are instrumental in understanding the dynamics of proteins and biomacromolecular complexes.

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