scholarly journals X-ray Natural Circular Dichroism Imaging of Multiferroic Crystals

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 531
Author(s):  
Mikhail S. Platunov ◽  
Irina A. Gudim ◽  
Elena N. Ovchinnikova ◽  
Ksenia A. Kozlovskaya ◽  
Fabrice Wilhelm ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
High Performance ◽  
Structural Changes ◽  
Visible Range ◽  
X Rays ◽  
Contrast Imaging ◽  
X Ray ◽  
Spatially Resolved ◽  
Circular Dichroïsm

The polarizing spectroscopy techniques in visible range optics have been used since the beginning of the 20th century to study the anisotropy of crystals based on birefringence and optical activity phenomena. On the other hand, the phenomenon of X-ray optical activity has been demonstrated only relatively recently. It is a selective probe for the element-specific properties of individual atoms in non-centrosymmetric materials. We report the X-ray Natural Circular Dichroism (XNCD) imaging technique which enables spatially resolved mapping of X-ray optical activity in non-centrosymmetric materials. As an example, we present the results of combining micro-focusing X-ray optics with circularly polarized hard X-rays to make a map of enantiomorphous twinning in a multiferroic SmFe3(BO3)4 crystal. Our results demonstrate the utility and potential of polarization-contrast imaging with XNCD as a sensitive technique for multiferroic crystals where the local enantiomorphous properties are especially important. In perspective, this brings a novel high-performance method for the characterization of structural changes associated with phase transitions and identification of the size and spatial distribution of twin domains.

Magnetic Structure of Multilayers from Soft-X-Ray Magnetic Circular Dichroism

1994 ◽  
Vol 375 ◽  
Author(s):  
C. T. Chen ◽  
Y. U. Idzerda ◽  
C.-C. Kao ◽  
L. H. Tjeng ◽  
H.-J. Lin ◽  
...  
Keyword(s):  
Thin Films ◽  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Magnetic Thin Films ◽  
X Rays ◽  
X Ray ◽  
Specific Manner ◽  
Left And Right ◽  
The Difference ◽  
Circular Dichroïsm

AbstractSoft-x-ray magnetic circular dichroism (MCD) is the difference between the absorptivity or reflectivity of left and right circularly polarized soft-x-rays at the magnetically interesting L2,3- edges of 3d transition metals or the M4,5-edges of the 4f rare earth elements. Thanks to its large absorption cross-section and strong MCD effect, this technique has become a powerful new means for probing, in an element- and site-specific manner, the magnetic properties of ultra-thin films and multilayers. Soft-x-ray MCD experiments, recently conducted at the Dragon beamline, are utilized to demonstrate the recent progress in this technique and its applications in the research of magnetic thin films.

Quarter-Wave Plates and X-ray Magnetic Circular Dichroism on ID24 at the ESRF

1998 ◽  
Vol 5 (5) ◽  
pp. 1298-1303 ◽  
Author(s):  
S. Pizzini ◽  
M. Bonfim ◽  
F. Baudelet ◽  
H. Tolentino ◽  
A. San Miguel ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Energy Dispersive ◽  
X Rays ◽  
X Ray ◽  
Diamond Crystals ◽  
Quarter Wave ◽  
Circular Dichroïsm

The first XMCD measurements carried out on the ID24 energy-dispersive XAS beamline at the ESRF are reported. Circular-polarized X-rays are obtained using perfect diamond crystals as quarter-wave plates. The very small source divergence allows circular polarizations close to unity to be obtained.

Optical anisotropy and sign reversal in layer-by-layer assembled films from chiral nanoparticles

2016 ◽  
Vol 191 ◽  
pp. 141-157 ◽  
Author(s):  
Zhumei Liang ◽  
Kalil Bernardino ◽  
Jishu Han ◽  
Yunlong Zhou ◽  
Kai Sun ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
Metallic Nanoparticles ◽  
Density Functional ◽  
Structural Changes ◽  
Building Blocks ◽  
Layer By Layer ◽  
Semiconductor Films ◽  
Surface Ligands ◽  
Circular Dichroïsm

Chiral anisotropy and related optical effects at the nanoscale represent some of the most dynamic areas of nanomaterials today. Translation of optical activity of chiral semiconductor and metallic nanoparticles (NPs) into optoelectronic devices requires preparation of thin films from chiral NPs on both flat and curved surfaces. In this paper we demonstrate that chiral NP films can be made via layer-by-layer assembly (LBL) using negatively charged chiral CdS NPs, stabilized by d- and l-cysteine and positively charged polyelectrolytes, as building blocks. LBL coatings from NPs combine simplicity of preparation and strong optical activity. Circular extinction measurements using circular dichroism instruments indicate that the film possess four chiroptical bands at 280, 320, 350, and 390 nm. The latter two bands at 390 and 350 nm are associated with the band gap transitions (chiral excitons), while the former two are attributed to transitions involving surface ligands. When NPs are assembled in LBL films, the rotatory activity and the sign for circular extinction associated with the electronic transition in the inorganic core of the NPs is conserved. However, this is not true for circular extinction bands at short wavelengths: the sign of the rotatory optical activity is reversed. This effect is attributed to the change of the conformation of surface ligands in the polyelectrolyte matrix, which was confirmed both by semi-empirical and density functional (DFT) quantum mechanical calculations. Circular dichroism spectra calculated using a DFT algorithm closely match the experimental spectra of CdS NPs. These findings indicate that the spectroscopic methods sensitive to chirality of the surface ligands can be used to investigate fine structural changes in the surface layer of nanocolloids. Strong rotatory optical activity of nanostructured semiconductor films opens the possibilities for new polarization-based optical devices.

X-ray magnetic circular dichroism imaging with hard X-rays

2001 ◽  
Vol 8 (3) ◽  
pp. 1021-1026 ◽  
Author(s):  
K. Sato ◽  
Y. Ueji ◽  
K. Okitsu ◽  
T. Matsushita ◽  
Y. Amemiya
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
X Rays ◽  
X Ray ◽  
Circular Dichroïsm

scholarly journals X-Ray Magnetic Circular Dichroism Spectroscopy and Microscopy

MRS Bulletin ◽  
1995 ◽  
Vol 20 (10) ◽  
pp. 41-44 ◽  
Author(s):  
N.V. Smith ◽  
H.A. Padmore
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
X Rays ◽  
Circularly Polarized ◽  
X Ray ◽  
Insertion Device ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Out Of Plane ◽  
X Ray Absorption ◽  
Circular Dichroïsm

The advent of electron accelerators dedicated to the production of high-intensity x-rays has revitalized experimental techniques based on x-ray absorption. A recent variant is to use circularly polarized x-rays generated either by use of out-of-plane radiation from a bending magnet or from a specially designed “insertion device.” This new field of x-ray magnetic circular dichroism (XMCD) shows considerable promise in spectroscopy and microscopy of magnetic materials. In this article, we describe the nature of XMCD, offer a few examples of recent progress, and review the prospects for future development using the newly constructed Advanced Light Source (ALS).

scholarly journals Resonance Raman Optical Activity Spectroscopy in Probing Structural Changes Invisible to Circular Dichroism Spectroscopy: A Study on Truncated Vitamin B12 Derivatives

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4386
Author(s):  
Ewa Machalska ◽  
Grzegorz Zajac ◽  
Monika Halat ◽  
Aleksandra J. Wierzba ◽  
Dorota Gryko ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Vitamin B12 ◽  
Optical Activity ◽  
Structural Changes ◽  
Resonance Condition ◽  
Resonance Raman Spectroscopy ◽  
Complex Structure ◽  
Resonance Raman ◽  
Raman Optical Activity ◽  
Circular Dichroïsm

This work demonstrates resonance Raman optical activity (RROA) spectra of three truncated vitamin B12 derivatives modified within the nucleotide loop. Since truncated cobalamins possess sufficiently high rotational strength in the range of ROA excitation (532 nm), it was possible to record their spectra in the resonance condition. They showed several distinct spectral features allowing for the distinguishing of studied compounds, in contrast to other methods, i.e., UV-Vis absorption, electronic circular dichroism, and resonance Raman spectroscopy. The improved capacity of the RROA method is based here on the excitation of molecules via more than two electronic states, giving rise to the bisignate RROA spectrum, significantly distinct from a parent Raman spectrum. This observation is an important step in the dissemination of using RROA spectroscopy in studying the complex structure of corrinoids which may prove crucial for a better understanding of their biological role.

scholarly journals Magnetic Circular Dichroism in X-Ray Absorption and Core-Level Photoemission

1993 ◽  
Vol 313 ◽  
Author(s):  
J.G. Tobin ◽  
G.D. Waddill ◽  
T.H. Gouder ◽  
C.A. Colmenares ◽  
D.P. Pappas
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Branching Ratio ◽  
Core Level ◽  
Magnetic Axis ◽  
X Rays ◽  
Circularly Polarized ◽  
X Ray ◽  
X Ray Absorption ◽  
Circular Dichroïsm

ABSTRACTHere is reported observation of magnetic circular dichroism in both x-ray absorption and core-level photoemission of ultra thin magnetic films using circularly polarized x-rays. Iron films (1–4 ML) grown on a Cu (001) substrate at 150 K and magnetized perpendicular to the surface show dramatic changes in the L2,3 absorption branching ratio for different x-ray polarizations. For linearly-polarized x-rays perpendicular to the magnetic axis of the sample the branching ratio was 0.75. For films ≥ 2 ML, this ratio varied from 0.64 to 0.85 for photon spin parallel and anti-parallel, respectively, to the magnetic axis. This effect was observed either by changing the x-ray helicity for a fixed magnetic axis, or by reversing the magnetic axis for a fixed x-ray helicity. Our observation can be analyzed within a simple one-electron picture, if the raw branching ratios are normalized so that the linear value becomes statistical. Furthermore, warming the films to -300 K eliminated this effect, indicating a loss of magnetization in the film over a temperature range of -30 K. Finally, reversing the relative orientation of the photon spin and the magnetic axis from parallel to anti-parallel allowed measurement with photoemission of the exchange splitting of the Fe 2p and 3p core levels which were found to be 03 eV and 0.2 eV, respectively. These results are consistent with earlier studies, but the use of off-plane circularly-polarized x-rays from a bending magnet monochromator offers -2 orders of magnitude greater intensity than typical spin-polarization measurements. Finally, we have performed preliminary x-ray absorption studies of UFe2, demonstrating the feasibilty of MCD Measurements in 5f as well as 3d Materials.

X-ray natural circular dichroism in langasite crystal

2018 ◽  
Vol 25 (1) ◽  
pp. 222-231 ◽  
Author(s):  
Alexey P. Oreshko ◽  
Elena N. Ovchinnikova ◽  
Andrei Rogalev ◽  
Fabrice Wilhelm ◽  
Boris V. Mill ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
Optical Axis ◽  
Electric Quadrupole ◽  
Quantum Mechanical ◽  
Opposite Parity ◽  
High Quality ◽  
X Ray ◽  
X Ray Absorption ◽  
Circular Dichroïsm

Optical activity in the X-ray range stems from the electric-dipole–electric-quadrupole interference terms mixing multipoles of opposite parity, and can be observed exclusively in systems with broken inversion symmetry. The gyration tensor formalism is used to describe the X-ray optical activity in langasite La3Ga5SiO14crystal with theP321 space group. An experimental study of the X-ray natural circular dichroism (XNCD) near the GaK-edge in La3Ga5SiO14single crystal was performed at ESRF beamline ID12, both along and perpendicular to the crystal optical axis. The combination of the quantum mechanical calculations and high-quality experimental results has allowed us to separate the contributions into X-ray absorption and XNCD spectra of Ga atoms occupying three distinct Wyckoff positions.

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