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.

Resonant and non-resonant magnetic scatterings with circularly polarized X-rays: magnetic scattering factor and electron density of gadolinium iron garnet

2017 ◽  
Vol 73 (3) ◽  
pp. 257-270 ◽  
Author(s):  
Yo Sasaki ◽  
Maki Okube ◽  
Satoshi Sasaki
Keyword(s):  
Electron Density ◽  
Magnetic Circular Dichroism ◽  
Experimental Studies ◽  
Magnetic Scattering ◽  
Unstable State ◽  
X Rays ◽  
Circularly Polarized ◽  
X Ray ◽  
Iron Garnet ◽  
Magnetic Electron

Theoretical and experimental studies on resonant magnetic scattering have been carried out using circularly polarized X-rays. Polarization dependence of the asymmetric ratio between right- and left-handed polarized scattering amplitudes has revealed that resonant and non-resonant magnetic scatterings can be observed simultaneously. In this study, synchrotron X-ray intensity experiments were conducted on Gd iron garnet (GdIG) at the pre-edge of the FeKabsorption edge. The asymmetric ratio between circular polarizations exhibited three peaks due to the resonant magnetic responses of Fe3+in the Fe2 (24d) site. These magnetic responses are antiparallel and have apparently higher resolution than dispersive X-ray magnetic circular dichroism at the pre-edge region; this can be mainly attributed to electric dipole transitions from 1stot2energy levels of the 3dorbitals in the tetrahedral symmetry in an unstable state quenched at higher temperature. Resonant magnetic scattering factorsf′mwere estimated from the asymmetric ratios. Fourier analysis was conducted using the intensity differences among circularly polarized X-rays at an energy ofE= 7.1085 keV. At this energy level, the characteristic distribution of magnetic electron density was clearly observed. This distribution was interpreted as a spin arrangement of Gd and Fe ions in GdIG. Also observed was the presence of hybridization of the magnetic electron orbitals as well as of the resonant magnetic Fe3+. The proposed method has the potential to be widely used in crystal structure analysis.

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 Magnetic electron density in Fe3O4 examined by RXMS at Fe K edge

2014 ◽  
Vol 70 (a1) ◽  
pp. C1555-C1555
Author(s):  
Satoshi Sasaki ◽  
Maki Okube ◽  
Shunichi Takayasu
Keyword(s):  
Crystal Structure ◽  
Fourier Series ◽  
Electron Density ◽  
Magnetic Scattering ◽  
Intensity Difference ◽  
X Rays ◽  
X Ray ◽  
Left Handed ◽  
Difference Fourier ◽  
Magnetic Electron

"It is known that a difference-Fourier synthesis of the Fourier series provides a mean for the location of bonding electrons, by subtracting out the electron density of all atoms in the crystal structure. Here the Fourier technique in X-ray diffraction was applied to observe the magnetic electron density of magnetite Fe3O4. An asymmetrical ratio in the resonant X-ray magnetic scattering (RXMS) provides information on the magnetic moments, which can be estimated from an intensity difference between the right-handed and left-handed polarized X rays. The ratio is proportional to the real part of the product of the spin-contributed structure factor F(hkl) and the complex conjugation of charge-scattered F(hkl). Expanding the equations in difference–Fourier formalization, the spin density can be represented with the observed f""m of RXMS. Synchrotron RXMS experiments were performed at the PF-BL-6C beamline using an AFC-5u four-circle diffractometer. Through a diamond phase retarder the incident X rays were circularly polarized at the Fe K absorption edge, where a wavelength of λ = 1.7439 Å (E = 7.1094 keV) was selected within the pre-edge. A spherical crystal of 0.13 mm in diameter was mounted along the a3 axis with the glass fiber on rare-earth magnet and goniometer head. The intensity data of RXMS were collected for Bragg reflections up to 2θ = 1310. After crystal-structure refinements with scaling of the RXMS data, difference-Fourier syntheses were made in triclinic symmetry with a total of 165 reflections by using the software FRAXY. The syntheses are superior in examining the magnetic effect in the polarization difference and eliminating other effects such as charge scattering, experimental errors and the termination effect. The difference of magnetic electron density between left-handed and right-handed circular polarizations at E was estimated in the Fourier series of partially observed F(hkl). The magnetic electron density on Fourier maps will be discussed in the presentation."

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 Design and performance of BOREAS, the beamline for resonant X-ray absorption and scattering experiments at the ALBA synchrotron light source

2016 ◽  
Vol 23 (6) ◽  
pp. 1507-1517 ◽  
Author(s):  
Alessandro Barla ◽  
Josep Nicolás ◽  
Daniele Cocco ◽  
Secundino Manuel Valvidares ◽  
Javier Herrero-Martín ◽  
...  
Keyword(s):  
Magnetic Circular Dichroism ◽  
Optical Design ◽  
Magnetic Scattering ◽  
Photon Flux ◽  
Optical Scheme ◽  
X Rays ◽  
X Ray ◽  
Sample Position ◽  
And Performance ◽  
X Ray Absorption

The optical design of the BOREAS beamline operating at the ALBA synchrotron radiation facility is described. BOREAS is dedicated to resonant X-ray absorption and scattering experiments using soft X-rays, in an unusually extended photon energy range from 80 to above 4000 eV, and with full polarization control. Its optical scheme includes a fixed-included-angle, variable-line-spacing grating monochromator and a pair of refocusing mirrors, equipped with benders, in a Kirkpatrick–Baez arrangement. It is equipped with two end-stations, one for X-ray magnetic circular dichroism and the other for resonant magnetic scattering. The commissioning results show that the expected beamline performance is achieved both in terms of energy resolution and of photon flux at the sample position.

scholarly journals Al-driven peculiarities of local coordination and magnetic properties in single-phase Alx-CrFeCoNi high-entropy alloys

Nano Research ◽  
2021 ◽  
Author(s):  
Alevtina Smekhova ◽  
Alexei Kuzmin ◽  
Konrad Siemensmeyer ◽  
Chen Luo ◽  
Kai Chen ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Magnetic Circular Dichroism ◽  
Surface Region ◽  
Face Centered Cubic ◽  
X Rays ◽  
X Ray ◽  
High Entropy ◽  
X Ray Absorption ◽  
Absorption Edges

AbstractModern design of superior multi-functional alloys composed of several principal components requires in-depth studies of their local structure for developing desired macroscopic properties. Herein, peculiarities of atomic arrangements on the local scale and electronic states of constituent elements in the single-phase face-centered cubic (fcc)- and body-centered cubic (bcc)-structured high-entropy Alx-CrFeCoNi alloys (x = 0.3 and 3, respectively) are explored by element-specific X-ray absorption spectroscopy in hard and soft X-ray energy ranges. Simulations based on the reverse Monte Carlo approach allow to perform a simultaneous fit of extended X-ray absorption fine structure spectra recorded at K absorption edges of each 3d constituent and to reconstruct the local environment within the first coordination shells of absorbers with high precision. The revealed unimodal and bimodal distributions of all five elements are in agreement with structure-dependent magnetic properties of studied alloys probed by magnetometry. A degree of surface atoms oxidation uncovered by soft X-rays suggests different kinetics of oxide formation for each type of constituents and has to be taken into account. X-ray magnetic circular dichroism technique employed at L2.3 absorption edges of transition metals demonstrates reduced magnetic moments of 3d metal constituents in the sub-surface region of in situ cleaned fcc-structured Al0.3-CrFeCoNi compared to their bulk values. Extended to nanostructured versions of multicomponent alloys, such studies would bring new insights related to effects of high entropy mixing on low dimensions.

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.

MAGNETIC MICROSPECTROSCOPY BY A COMBINATION OF XMCD AND PEEM

2002 ◽  
Vol 09 (02) ◽  
pp. 877-881 ◽  
Author(s):  
S. IMADA ◽  
S. SUGA ◽  
W. KUCH ◽  
J. KIRSCHNER
Keyword(s):  
Circular Dichroism ◽  
Full Advantage ◽  
Quantitative Evaluation ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
Magnetic Domain ◽  
X Ray ◽  
Circular Dichroïsm

The benefits of combining soft X-ray magnetic circular dichroism and photoelectron microscopy are demonstrated by applying this combination (XMCD–PEEM) not only to magnetic domain imaging but also to quantitative evaluation of the distribution of spin and orbital magnetic moments. The latter takes full advantage of the spectroscopic aspect of XMCD–PEEM.

scholarly journals Hard X-ray polarizer to enable simultaneous three-dimensional nanoscale imaging of magnetic structure and lattice strain

2016 ◽  
Vol 23 (5) ◽  
pp. 1210-1215 ◽  
Author(s):  
Jonathan Logan ◽  
Ross Harder ◽  
Luxi Li ◽  
Daniel Haskel ◽  
Pice Chen ◽  
...  
Keyword(s):  
Magnetic Circular Dichroism ◽  
Three Dimensional ◽  
Control Sample ◽  
Magnetic Ordering ◽  
X Rays ◽  
Diffractive Imaging ◽  
X Ray ◽  
Coherent Diffractive Imaging ◽  
Diffraction Patterns ◽  
A New Technique

Recent progress in the development of dichroic Bragg coherent diffractive imaging, a new technique for simultaneous three-dimensional imaging of strain and magnetization at the nanoscale, is reported. This progress includes the installation of a diamond X-ray phase retarder at beamline 34-ID-C of the Advanced Photon Source. The performance of the phase retarder for tuning X-ray polarization is demonstrated with temperature-dependent X-ray magnetic circular dichroism measurements on a gadolinium foil in transmission and on a Gd5Si2Ge2crystal in diffraction geometry with a partially coherent, focused X-ray beam. Feasibility tests for dichroic Bragg coherent diffractive imaging are presented. These tests include (1) using conventional Bragg coherent diffractive imaging to determine whether the phase retarder introduces aberrations using a nonmagnetic gold nanocrystal as a control sample, and (2) collecting coherent diffraction patterns of a magnetic Gd5Si2Ge2nanocrystal with left- and right-circularly polarized X-rays. Future applications of dichroic Bragg coherent diffractive imaging for the correlation of strain and lattice defects with magnetic ordering and inhomogeneities are considered.

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.

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