Site-specific electronic structures of ferrimagnetic Fe3O4 measured by resonant X-ray magnetic scattering

2014 ◽  
Vol 47 (4) ◽  
pp. 1387-1394 ◽  
Author(s):  
Maki Okube ◽  
Satoshi Sasaki
Keyword(s):  
Electronic Structures ◽  
Magnetic Moments ◽  
Energy Levels ◽  
Magnetic Scattering ◽  
Local Spin Density Approximation ◽  
X Rays ◽  
Fourier Synthesis ◽  
Site Specific ◽  
X Ray ◽  
Energy Dependent

Resonant magnetic scattering of circularly polarized synchrotron X-rays has revealed the site-specific magnetic moments at two non-equivalent Fe ion sites in Fe3O4. The energy-dependent peaks for the 026 and 266 reflections were attributed ferrimagnetically to the e and t 2 energy levels of Fe 3d at the A site, and to the t 2g and e g levels at the B site, respectively, having a sequence of t 2g, e, e g and t 2 in order of energy. This sequence agrees with the local spin-density approximation calculations in the literature [Anisimov, Elfimov, Hamada & Terakura, (1996). Phys. Rev. 54, 4387–4390], in which the spin-down band at the Fermi energy corresponds to t 2g . Resonant magnetic Fourier synthesis reveals the electron densities of the ferrimagnetic moments.

scholarly journals Site-specific RXMS study on the magnetic electron of magnetite

2014 ◽  
Vol 70 (a1) ◽  
pp. C1368-C1368
Author(s):  
Maki Okube ◽  
Satoshi Sasaki
Keyword(s):  
Magnetic Circular Dichroism ◽  
Energy State ◽  
Magnetic Moments ◽  
Form Factors ◽  
Magnetic Scattering ◽  
Orbital Interaction ◽  
X Rays ◽  
Density Of State ◽  
X Ray ◽  
Magnetic Electron

Magnetite Fe3O4 is the best known magnetic mineral for its attractive properties for various magnetic applications. The magnetic moments of Fe atoms show a collinear ferrimagnetic ordering between tetrahedral A and octahedral B sites in an inverse spinel structure with the chemical formula of [Fe3+]A[Fe2+Fe3+]BO4. The distribution of the Fe2+ and Fe3+ over A and B sites is determined by a delicate balance of the crystal field. The geometrical environment of 3d transition metals strongly affects the distribution and the energy state of magnetic electrons which contributes magnetic moments. The resonant x-ray magnetic scattering (RXMS) allows us to make site-selective structural analysis with respect to the magnetic electron. In order to clarify the behavior of the magnetic electrons in magnetite, we carried out the energy-dependent RXMS near Fe K edge. Depends on the observation related to 3d-4p electric transition to empty bands of unpaired electron, we studied the orbital interaction and the density of state of magnetic electrons in A site and B site of magnetite independently. RXMS intensity measurements were performed by using Rigaku AFC-5u four-circle diffractometers at BL-6C of Photon Factory. Circularly-polarized X-rays were produced by a transmitted-type phase retarder of diamond (111). According to the X-ray magnetic circular dichroism (XMCD) spectrum at the Fe K edge, 48 x-ray energies to perform RXMS measurement were selected. The magnetic form factors for various energies were calculated from the difference in diffraction intensities between left- and right-circular polarized measurements. By examining the energy dependence of the resonant magnetic peaks, the density of state of 3d magnetic electron of Fe were obtained for A and B site through the experimental analysis. In the presentation, the interrelationship between the site geometry and the magnetic electrons in terms of energy state will be discussed.

about chemical bonding and molecular structure. This information can be used to detect th e types of organic materials present on the surface. 4.3.2.2. Raman spectroscopy (RS) [7, 8] It is used to examine the energy levels of molecules that cannot be well character-ized via infrared spectroscopy. Th e two techniques, however, are complimentary. In the RS, a sample is irradiated with a strong monochromatic light source (usu-ally a laser). Most of the radiation will scatter or "reflect off' the sample at the same energy as the incoming laser radiation. However, a small amount will scat-ter from the sample at a wavelength slightly shifted from the original wavelength. It is possible to study the molecular structure or determine the chemical identity of the sample. It is quite straightforward to identify compounds by spectral library search. Due to extensive library spectral information, the unique spectral finger-print of every compound, and the ease with which such analyses can be per-formed, the RS is a very useful technique for various applications. An important application of the RS is the rapid, nondestructive characterization of diamond, diamond-like, and amorphous-carbon films. 4.3.2.3. Scanning electron microscopy (SEM) / energy dispersive X-ra y analysis (EDX) [7, 8] The SEM produce s detailed photographs that provide important information about the surface structure and morphology of almost any kind of sample. Image analy-sis is often the first and most important step in problem solving and failure analy-sis. With SEM, a focused beam of high-energy electrons is scanned over the sur-face of a material, causing a variety of signals, secondary electrons, X-rays, photons, etc. - each of which may be used to characterize the material with re-spect to specific properties . The signals are used to modulate the brightness on a CRT display, thereb y providing a high-resolution map of the selected material property. It is a surface imaging technique, but with Energy Dispersive X-ray (EDX) it can identify elements in the near-surface region. This technique is most useful for imaging particles. 4.3.2.4. X-ray fluorescence (XRF) [7, 8] Incident X-rays are used to excite surface atoms. The atoms relax through the emission of an X-ray with energy characteristic of the parent atoms and the inten-sity proportional to the amount of the element present. It is a bulk or "total mate-rials" characterization technique for rapid, simultaneous, and nondestructive analysis of elements having an atomic number higher than that of boron. Tradi-tional bulk analysis applications include identifying metals and alloys, detecting trace elements in liquids, and identifying residues and deposits. 4.3.2.5. Total-reflection X-ray fluorescence (TXRF) [7, 8] It is a special XRF technique that provides extremely sensitive measures of the elements present in a material's outer surface. Applications include searching for metal contamination in thin films on silicon wafers and detecting picogram-levels o f arsenic, lead, mercury and cadmium on hazardous, chemical fume hoods.

2003 ◽  
pp. 43-45
Keyword(s):  
Molecular Structure ◽  
Energy Levels ◽  
Monochromatic Light ◽  
Surface Region ◽  
Carbon Films ◽  
Energy Dispersive ◽  
X Rays ◽  
Bulk Analysis ◽  
X Ray ◽  
High Resolution Map

scholarly journals Magnetic X-Ray Circular Dichroism in Spin-Polarized Photoelectron Diffraction

1994 ◽  
Vol 375 ◽  
Author(s):  
G. D. Waddill ◽  
J. G. Tobin ◽  
X. Guo ◽  
S. Y. Tong
Keyword(s):  
Magnetic Structure ◽  
Multiple Scattering ◽  
Analytical Procedure ◽  
Structural Determination ◽  
X Rays ◽  
Circularly Polarized ◽  
X Ray ◽  
Photoelectron Diffraction ◽  
Spin Polarized ◽  
Energy Dependent

AbstractThe first structural determination with spin-polarized, energy-dependent photoelectron diffraction using circularly-polarized x-rays is reported for Fe films on Cu(001). Circularly-polarized x-rays produce spin-polarized photoelectrons from the Fe 2p doublet, and intensity asymmetries in the 2p3/2 level are observed. Fully spin-specific multiple scattering calculations reproduce the experimentally-determined energy and angular dependences. A new analytical procedure which focuses upon intensity variations due to spin-dependent diffraction is introduced. A sensitivity to local geometric and magnetic structure is demonstrated.

Energy-dependent polarization study of the x-ray magnetic scattering in terbium metal

1998 ◽  
Vol 10 (9) ◽  
pp. 1951-1964 ◽  
Author(s):  
S C Perry ◽  
M M R Costa ◽  
W G Stirling ◽  
M J Longfield ◽  
D Mannix ◽  
...  
Keyword(s):  
Magnetic Scattering ◽  
X Ray ◽  
Polarization Study ◽  
Dependent Polarization ◽  
Energy Dependent

scholarly journals Iodine containing porous organosilica nanoparticles trigger tumor spheroids destruction upon monochromatic X-ray irradiation: DNA breaks and K-edge energy X-ray

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuya Higashi ◽  
Kotaro Matsumoto ◽  
Hiroyuki Saitoh ◽  
Ayumi Shiro ◽  
Yue Ma ◽  
...  
Keyword(s):  
Mesoporous Silica Nanoparticles ◽  
Energy Levels ◽  
Tumor Spheroid ◽  
X Rays ◽  
Apoptosis Induction ◽  
Dna Breaks ◽  
Tumor Spheroids ◽  
X Ray ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

AbstractX-ray irradiation of high Z elements causes photoelectric effects that include the release of Auger electrons that can induce localized DNA breaks. We have previously established a tumor spheroid-based assay that used gadolinium containing mesoporous silica nanoparticles and synchrotron-generated monochromatic X-rays. In this work, we focused on iodine and synthesized iodine-containing porous organosilica (IPO) nanoparticles. IPO were loaded onto tumor spheroids and the spheroids were irradiated with 33.2 keV monochromatic X-ray. After incubation in CO2 incubator, destruction of tumor spheroids was observed which was accompanied by apoptosis induction, as determined by the TUNEL assay. By employing the γH2AX assay, we detected double strand DNA cleavages immediately after the irradiation. These results suggest that IPO first generate double strand DNA breaks upon X-ray irradiation followed by apoptosis induction of cancer cells. Use of three different monochromatic X-rays having energy levels of 33.0, 33.2 and 33.4 keV as well as X-rays with 0.1 keV energy intervals showed that the optimum effect of all three events (spheroid destruction, apoptosis induction and generation of double strand DNA breaks) occurred with a 33.2 keV monochromatic X-ray. These results uncover the preferential effect of K-edge energy X-ray for tumor spheroid destruction mediated by iodine containing nanoparticles.

scholarly journals Perspectives towards Sub-Ångström Working Regime of the European X-ray Free-Electron Laser with Low-Emittance Electron Beams

2021 ◽  
Vol 11 (22) ◽  
pp. 10768
Author(s):  
Ye Chen ◽  
Frank Brinker ◽  
Winfried Decking ◽  
Matthias Scholz ◽  
Lutz Winkelmann
Keyword(s):  
Electron Beam ◽  
Photon Energy ◽  
Free Electron ◽  
Free Electron Laser ◽  
Electron Beams ◽  
Energy Levels ◽  
Energetic Electron ◽  
X Rays ◽  
X Ray ◽  
Low Emittance

Sub-ångström working regime refers to a working state of free-electron lasers which allows the generation of hard X-rays at a photon wavelength of 1 ångström and below, that is, a photon energy of 12.5 keV and above. It is demonstrated that the accelerators of the European X-ray Free-Electron Laser can provide highly energetic electron beams of up to 17.5 GeV. Along with long variable-gap undulators, the facility offers superior conditions for exploring self-amplified spontaneous emission (SASE) in the sub-ångström regime. However, the overall FEL performance relies quantitatively on achievable electron beam qualities through a kilometers-long accelerator beamline. Low-emittance electron beam production and the associated start-to-end beam physics thus becomes a prerequisite to dig in the potentials of SASE performance towards higher photon energies. In this article, we present the obtained results on electron beam qualities produced with different accelerating gradients of 40 MV/m–56 MV/m at the cathode, as well as the final beam qualities in front of the undulators via start-to-end simulations considering realistic conditions. SASE studies in the sub-ångström regime, using optimized electron beams, are carried out at varied energy levels according to the present state of the facility, that is, a pulsed mode operating with a 10 Hz-repetition 0.65 ms-long bunch train energized to 14 GeV and 17.5 GeV. Millijoule-level SASE intensity is obtained at a photon energy of 25 keV at 14 GeV electron beam energy using a gain length of about 7 m. At 17.5 GeV, half-millijoule lasing is achieved at 40 keV. Lasing at up to 50 keV is demonstrated with pulse energies in the range of a few hundreds and tens of microjoules with existing undulators and currently achievable electron beam qualities.

scholarly journals RESONANT MAGNETIC SCATTERING OF POLARIZED SOFT X-RAYS

2000 ◽  
Vol 07 (01n02) ◽  
pp. 175-189 ◽  
Author(s):  
MAURIZIO SACCHI
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Elastic Scattering ◽  
Synchrotron Radiation ◽  
Energy Range ◽  
Magnetic Scattering ◽  
X Rays ◽  
X Ray ◽  
Magnetic Devices ◽  
Recent Extension

Resonant elastic scattering of polarized X-rays is a powerful technique for the study of the magnetic properties of solids. Its recent extension to the soft X-ray energy range has been driven by applications in the field of artificially structured magnetic devices, like multilayers and superlattices. This article reviews recent elastic scattering experiments using synchrotron radiation, performed at the 2p core resonances of transition metals in solids, thin films and ordered multilayers.

scholarly journals Measuring non-equilibrium dynamics in complex solids with ultrashort X-ray pulses

2019 ◽  
Vol 377 (2145) ◽  
pp. 20170478 ◽  
Author(s):  
Michele Buzzi ◽  
Michael Först ◽  
Andrea Cavalleri
Keyword(s):  
Electronic Structures ◽  
Research Trend ◽  
Strong Interactions ◽  
X Rays ◽  
X Ray Diffraction ◽  
Optical Pulses ◽  
Time Resolved ◽  
X Ray ◽  
Equilibrium Dynamics ◽  
External Perturbations

Strong interactions between electrons give rise to the complexity of quantum materials, which exhibit exotic functional properties and extreme susceptibility to external perturbations. A growing research trend involves the study of these materials away from equilibrium, especially in cases in which the stimulation with optical pulses can coherently enhance cooperative orders. Time-resolved X-ray probes are integral to this type of research, as they can be used to track atomic and electronic structures as they evolve on ultrafast timescales. Here, we review a series of recent experiments where femtosecond X-ray diffraction was used to measure dynamics of complex solids. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

scholarly journals STATE OFCoANDMnIN HALF-METALLIC FERROMAGNETCo2MnSiEXPLORED BY MAGNETIC CIRCULAR DICHROISM IN HARD X-RAY PHOTOELECTRON EMISSION AND SOFT X-RAY ABSORPTION SPECTROSCOPIES

SPIN ◽  
2014 ◽  
Vol 04 (04) ◽  
pp. 1440017 ◽  
Author(s):  
GERHARD H. FECHER ◽  
DANIEL EBKE ◽  
SIHAM OUARDI ◽  
STEFANO AGRESTINI ◽  
CHANG-YANG KUO ◽  
...  
Keyword(s):  
Magnetic Moment ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
Magnetic Behavior ◽  
Photoelectron Spectra ◽  
X Rays ◽  
Half Metallic ◽  
X Ray ◽  
Magnetic Dichroism ◽  
X Ray Absorption

The half-metallic Heusler compound Co2MnSi is a very attractive material for spintronic devices because it exhibits very high tunnelling magnetoresistance ratios. This work reports on a spectroscopic investigation of thin Co2MnSi films as they are used as electrodes in magnetic tunnel junctions. The investigated films exhibit a remanent in-plane magnetization with a magnetic moment of about 5 μBwhen saturated, as expected. The low coercive field of only 4 mT indicates soft magnetic behavior. Magnetic dichroism in emission and absorption was measured at the Co and Mn  2p core levels. The photoelectron spectra were excited by circularly polarized hard X-rays with an energy of 6 keV and taken from the remanently magnetized film. The soft X-ray absorption spectra were taken in an induction field of 4 T. Both methods yielded large dichroism effects. An analysis reveals the localized character of the electrons and magnetic moments attributed to the Mn atoms, whereas the electrons related to the Co atoms contribute an itinerant part to the total magnetic moment.

scholarly journals Mapping domains in the weak ferromagnet CoCO3

2014 ◽  
Vol 70 (a1) ◽  
pp. C1356-C1356
Author(s):  
Guillaume Beutier ◽  
Steve Collins ◽  
Gareth Nisbet ◽  
Elena Ovchinnikova ◽  
Vladimir Dmitrienko
Keyword(s):  
Magnetic Moments ◽  
Electric Polarization ◽  
Magnetic Scattering ◽  
Zero Field ◽  
Dm Interaction ◽  
X Ray ◽  
Absolute Orientation ◽  
Weak Ferromagnet ◽  
The Absolute ◽  
Perpendicular Component

The Dzyaloshinskii-Moriya (DM) interaction [1,2] produces a perpendicular component in the coupling of neighbouring spins when the symmetry between the spins is low, or can drive a distortion of intervening atoms to create a spontaneous electric polarization in some magnetoelectrics. In weak ferromagnets, the canting of the atomic moments due to the DM interaction leads to a small parasitic ferromagnetic polarization in an otherwise antiferromagnetic structure. Recently, we determined the sign of the Dzyaloshinskii–Moriya interaction in the weak ferromagnet FeBO3 by measuring the interference between resonant x-ray scattering and non-resonant magnetic scattering at a forbidden reflection [3]. Using the same method, we determine its sign in the carbonates MnCO3 and CoCO3. These isostructural materials turn out to show opposite interference effect: further analysis is underway to confirm or not that they actually have Dzyaloshinskii–Moriya interactions of opposite signs. We go one step further and apply the same principle to map the absolute orientation (direction and sense) of the magnetisation in a crystal of CoCO3: by mapping the 009 forbidden reflection at 3 azimuthal angles, we obtain 3 projections of the local magnetisation allowing its unambiguous determination. The reconstructed magnetisation map, whose spacial resolution is about 20 µm x 20 µm (the size of the focused x-ray beam), was measured after zero-field cooling to 9 K, well below the Neel temperature. It confirms the strong in-plane anisotropy of the material, with magnetisation domains essentially along 6 orientations separated by 600. Two of them, with orientation at 600to each other (green and orange in the figure), are largely dominant on the part of the sample that was imaged. To our knowledge it is the first experimental determination of the absolute orientation of the magnetic moments in a weak ferromagnet. The figure shows the reconstructed map of magnetisation, with the direction of the local in-plane magnetisation encoded (in radians) on a periodic colour map.

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