Interplay between Local Electronic Structure, Crystalline Structure and Magnetic Ordering in Intermetallic Compounds Ce2Fe17−xMnx

2012 ◽  
Vol 190 ◽  
pp. 251-254 ◽  
Author(s):  
Alexander A. Yaroslavtsev ◽  
Alexey P. Menushenkov ◽  
Olga V. Grishina ◽  
Roman V. Chernikov ◽  
Anatoly G. Kuchin
Keyword(s):  
Crystalline Structure ◽  
Magnetic Ordering ◽  
Local Environment ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
Magnetic States ◽  
First Time ◽  
X Ray Absorption ◽  
Mn Concentration

For the first time the rearrangement of cerium local environment in Ce2Fe17-xMnx(x = 0; 1; 2) intermetallics vs. Mn concentration and temperature was investigated by thespectroscopy of extended X-ray absorption fine structure (EXAFS) above K-Ce absorptionedge. At the same time under similar conditions by the spectroscopy of X-ray absorption near-edge structure (XANES) above L3-Ce absorption edge the valence state of Ce was studied. Thecorrelation is found between changes in local electronic and crystalline structure observed inCe2Fe17-xMnx and the types of magnetic states in these compounds.

scholarly journals Revealing noncollinear magnetic ordering at the atomic scale via XMCD

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fridtjof Kielgast ◽  
Ivan Baev ◽  
Torben Beeck ◽  
Federico Pressacco ◽  
Michael Martins
Keyword(s):  
Ground State ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Atomic Scale ◽  
Angle Of Incidence ◽  
X Ray ◽  
First Time ◽  
X Ray Absorption ◽  
Magnetic Sublattices

AbstractMass-selected V and Fe monomers, as well as the heterodimer $${\text{Fe}}_1{\text{V}}_1$$ Fe 1 V 1 , were deposited on a Cu(001) surface. Their electronic and magnetic properties were investigated via X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopy. Anisotropies in the magnetic moments of the deposited species could be examined by means of angle resolving XMCD, i.e. changing the X-ray angle of incidence. A weak adatom-substrate-coupling was found for both elements and, using group theoretical arguments, the ground state symmetries of the adatoms were determined. For the dimer, a switching from antiparallel to parallel orientation of the respective magnetic moments was observed. We show that this is due to the existence of a noncollinear spin-flop phase in the deposited dimers, which could be observed for the first time in such a small system. Making use of the two magnetic sublattices model, we were able to find the relative orientations for the dimer magnetic moments for different incidence angles.

X-ray absorption near edge structures in cobalt oxides

1996 ◽  
Vol 11 (9) ◽  
pp. 2242-2256 ◽  
Author(s):  
T. Jiang ◽  
D. E. Ellis
Keyword(s):  
Wave Functions ◽  
Site Symmetry ◽  
Local Geometry ◽  
Final State ◽  
Cluster Technique ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
Edge Features ◽  
X Ray Absorption

Theoretical studies have been made of K-edge x-ray absorption near edge structure (XANES) of Co in CoO, Co(OH)2, CoTiO3, Co3O4, and CoAl2O4. Correlations of experimental near edge features with site symmetry, local geometry, local electronic structure, i.e., atomic configuration, charge transfer, and backscattering from neighboring atomic potentials are interpreted. The self-consistent Discrete Variational Xa Method (DV-Xα) within an embedded cluster technique has been used to generate the crystal potential. A multiple scattering (MS) approach is then used to solve for the final state wave function. The ground state DV wave functions are analyzed in terms of the projected density of states, whereas the final state MS continuum wave functions are analyzed through the concept of photoelectron trapping time.

scholarly journals Local and electronic structure around Ga in CdTe: evidence of DX- and A-centers

2012 ◽  
Vol 20 (1) ◽  
pp. 166-171
Author(s):  
Vasil Koteski ◽  
Jelena Belošević-Čavor ◽  
Petro Fochuk ◽  
Heinz-Eberhard Mahnke
Keyword(s):  
Density Functional ◽  
Plane Waves ◽  
Lattice Relaxation ◽  
Defect Structures ◽  
Functional Theory ◽  
Edge Structure ◽  
X Ray ◽  
First Time ◽  
X Ray Absorption ◽  
Good Agreement

The lattice relaxation around Ga in CdTe is investigated by means of extended X-ray absorption spectroscopy (EXAFS) and density functional theory (DFT) calculations using the linear augmented plane waves plus local orbitals (LAPW+lo) method. In addition to the substitutional position, the calculations are performed for DX- and A-centers of Ga in CdTe. The results of the calculations are in good agreement with the experimental data, as obtained from EXAFS and X-ray absorption near-edge structure (XANES). They allow the experimental identification of several defect structures in CdTe. In particular, direct experimental evidence for the existence of DX-centers in CdTe is provided, and for the first time the local bond lengths of this defect are measured directly.

Local electronic structure of ZnS and ZnSe doped by Mn, Fe, Co, and Ni from x-ray-absorption near-edge structure studies

1996 ◽  
Vol 53 (3) ◽  
pp. 1119-1128 ◽  
Author(s):  
K. L/awniczak-Jabl/onska ◽  
R. J. Iwanowski ◽  
Z. Gol/acki ◽  
A. Traverse ◽  
S. Pizzini ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
X Ray Absorption

High-accuracy X-ray absorption spectra from mMsolutions of nickel (II) complexes with multiple solutions using transmission XAS

2015 ◽  
Vol 22 (4) ◽  
pp. 1008-1021 ◽  
Author(s):  
Christopher T. Chantler ◽  
M. Tauhidul Islam ◽  
Stephen P. Best ◽  
Lachlan J. Tantau ◽  
Chanh Q. Tran ◽  
...  
Keyword(s):  
Multiple Solutions ◽  
High Accuracy ◽  
Hybrid Technique ◽  
Edge Structure ◽  
New Approach ◽  
X Ray ◽  
Square Planar ◽  
Transmission Measurements ◽  
First Time ◽  
X Ray Absorption

A new approach is introduced for determining X-ray absorption spectroscopy (XAS) spectra on absolute and relative scales using multiple solutions with different concentrations by the characterization and correction of experimental systematics. This hybrid technique is a development of standard X-ray absorption fine structure (XAFS) along the lines of the high-accuracy X-ray extended range technique (XERT) but with applicability to solutions, dilute systems and cold cell environments. This methodology has been applied to determining absolute XAS of bis(N-n-propyl-salicylaldiminato) nickel(II) and bis(N-i-propyl-salicylaldiminato) nickel(II) complexes with square planar and tetrahedral structures in 15 mMand 1.5 mMdilute solutions. It is demonstrated that transmission XAS from dilute systems can provide excellent X-ray absorption near-edge structure (XANES) and XAFS spectra, and that transmission measurements can provide accurate measurement of subtle differences including coordination geometries. For the first time, (transmission) XAS of the isomers have been determined from low-concentration solutions on an absolute scale with a 1–5% accuracy, and with relative precision of 0.1% to 0.2% in the active XANES and XAFS regions after inclusion of systematic corrections.

scholarly journals XANES Measurements for Studies of Adsorbed Protein Layers at Liquid Interfaces

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4635
Author(s):  
Oleg V. Konovalov ◽  
Natalia N. Novikova ◽  
Mikhail V. Kovalchuk ◽  
Galina E. Yalovega ◽  
Alexey F. Topunov ◽  
...  
Keyword(s):  
Metal Binding ◽  
Radiation Condition ◽  
Liquid Interfaces ◽  
Radiation Load ◽  
Edge Structure ◽  
Site Structure ◽  
X Ray ◽  
Zinc Coordination ◽  
First Time ◽  
X Ray Absorption

X-ray absorption near edge structure (XANES) spectra for protein layers adsorbed at liquid interfaces in a Langmuir trough have been recorded for the first time. We studied the parkin protein (so-called E3 ubiquitin ligase), which plays an important role in pathogenesis of Parkinson disease. Parkin contains eight Zn binding sites, consisting of cysteine and histidine residues in a tetracoordinated geometry. Zn K-edge XANES spectra were collected in the following two series: under mild radiation condition of measurements (short exposition time) and with high X-ray radiation load. XANES fingerprint analysis was applied to obtain information on ligand environments around zinc ions. Two types of zinc coordination geometry were identified depending on X-ray radiation load. We found that, under mild conditions, local zinc environment in our parkin preparations was very similar to that identified in hemoglobin, treated with a solution of ZnCl2 salt. Under high X-ray radiation load, considerable changes in the zinc site structure were observed; local zinc environment appeared to be almost identical to that defined in Zn-containing enzyme alkaline phosphatase. The formation of a similar metal site in unrelated protein molecules, observed in our experiments, highlights the significance of metal binding templates as essential structural modules in protein macromolecules.

scholarly journals The Role of Structural Representation in the Performance of a Deep Neural Network for X-ray Spectroscopy

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2715
Author(s):  
Marwah M.M. Madkhali ◽  
Conor D. Rankine ◽  
Thomas J. Penfold
Keyword(s):  
Neural Network ◽  
Deep Neural Network ◽  
Mean Squared Error ◽  
Chemical Space ◽  
Theoretical Calculations ◽  
Local Environment ◽  
Structural Representation ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

An important consideration when developing a deep neural network (DNN) for the prediction of molecular properties is the representation of the chemical space. Herein we explore the effect of the representation on the performance of our DNN engineered to predict Fe K-edge X-ray absorption near-edge structure (XANES) spectra, and address the question: How important is the choice of representation for the local environment around an arbitrary Fe absorption site? Using two popular representations of chemical space—the Coulomb matrix (CM) and pair-distribution/radial distribution curve (RDC)—we investigate the effect that the choice of representation has on the performance of our DNN. While CM and RDC featurisation are demonstrably robust descriptors, it is possible to obtain a smaller mean squared error (MSE) between the target and estimated XANES spectra when using RDC featurisation, and converge to this state a) faster and b) using fewer data samples. This is advantageous for future extension of our DNN to other X-ray absorption edges, and for reoptimisation of our DNN to reproduce results from higher levels of theory. In the latter case, dataset sizes will be limited more strongly by the resource-intensive nature of the underlying theoretical calculations.

scholarly journals The local environment of metal sites in intracellular granules investigated by using X-ray-absorption spectroscopy

1984 ◽  
Vol 221 (3) ◽  
pp. 855-868 ◽  
Author(s):  
G N Greaves ◽  
K Simkiss ◽  
M Taylor ◽  
N Binsted
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
Nearest Neighbour ◽  
Model Compounds ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Oxygen Bond ◽  
Phosphate Deposits ◽  
Phosphate Groups

We report the use of X-ray-absorption spectroscopy (x.a.s.) to study the local atomic environment of cations in intracellular granules from the hepatopancreas of Helix aspersa. Both the calcium K-edge in these concretions and the manganese K-edge in doped specimens were measured. Electron-microprobe measurements confirm that the introduced Mn2+ is concentrated in irregular growths on the surfaces of the granules. The near-edge structure (x.a.n.e.s.) of calcium is similar to that of manganese, indicating that the oxygen-co-ordination spheres of both cations share a similar symmetry. From the extended structure (e.x.a.f.s.) the metal-oxygen bond lengths of 0.230 nm (2.30A) for Ca-O and 0.218 nm (2.18A) for Mn-O [+/- 0.004 nm (0.04A)] were determined, reference being made to a variety of model compounds. The low density of the granules (2.07 g/cm3), together with the local atomic distribution, suggest an open hydrated structure for these phosphate deposits. Detailed analysis of the distribution of nearest-neighbour oxygen atoms demonstrates that this is asymmetric and considerably broader for Ca2+ than for Mn2+. Compared with the model compounds, the Ca2+ environment in the granules is similar to that observed in Ca2P2O7. I.r. spectra indicate the presence of condensed phosphate groups in the granules, with the strong possibility these are pyrophosphate (P2O7(4-) groups.

X-ray absorption near-edge structure of GaN with high Mn concentration grown on SiC

2009 ◽  
Vol 21 (29) ◽  
pp. 295801 ◽  
Author(s):  
O Sancho-Juan ◽  
A Cantarero ◽  
N Garro ◽  
A Cros ◽  
G Martínez-Criado ◽  
...  
Keyword(s):  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Mn Concentration
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