649 research outputs found
Comment on ``Spin Polarization and Magnetic Circular Dichroism in Photoemission from the 2p Core Level of Ferromagnetic Ni''
Although the Ni_4 cluster includes more information regarding the Ni band
structure with respect to the Anderson impurity model, it also favors very
peculiar ground states which are incompatible with a coherent picture of all
dichroism experiments.Comment: 1 page, RevTeX, 1 epsf figur
Magnetic x‐ray dichroism of rare‐earth materials
We discuss recent developments in the magnetic x‐ray dichroism of rare‐earth materials. The application of this technique to the study of magnetic materials is discussed. Also, other work on magneto‐optical effects in the x‐ray range is reviewed
Magnetic circular dichroism of x-ray absorption spectroscopy at rare-earth L2,3 edges in RE2Fe14B compounds (RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)
Magnetic circular dichroism (MCD) in the x-ray absorption spectroscopy (XAS)
at the L2,3 edges for almost entire series of rare-earth (RE) elements in
RE2Fe14B, is studied experimentally and theoretically. By a quantitative
comparison of the complicated MCD spectral shapes, we find that (i) the 4f-5d
intra-atomic exchange interaction not only induces the spin and orbital
polarization of the 5d states, which is vital for the MCD spectra of the
electric dipole transition from the 2p core states to the empty 5d conduction
band, but also it accompanies a contraction of the radial part of the 5d wave
function depending on its spin and orbital state, which results in the
enhancement of the 2p-5d dipole matrix element, (ii) there are cases where the
spin polarization of the 5d states due to the hybridization with the spin
polarized 3d states of surrounding irons plays important roles, and (iii) the
electric quadrupole transition from the 2p core states to the magnetic vale!
nce 4f states is appreciable at the pre-edge region of the dipole spectrum.
Especially, our results evidence that it is important to include the
enhancement effect of the dipole matrix element in the correct interpretation
of the MCD spectra at the RE L2,3 edges.Comment: 9 pages, 5 figures, 1 table, REVTe
Band-theoretical prediction of magnetic anisotropy in uranium monochalcogenides
Magnetic anisotropy of uranium monochalcogenides, US, USe and UTe, is studied
by means of fully-relativistic spin-polarized band structure calculations
within the local spin-density approximation. It is found that the size of the
magnetic anisotropy is fairly large (about 10 meV/unit formula), which is
comparable with experiment. This strong anisotropy is discussed in view of a
pseudo-gap formation, of which crucial ingredients are the exchange splitting
of U 5f states and their hybridization with chalcogen p states (f-p
hybridization). An anomalous trend in the anisotropy is found in the series
(US>>USe<UTe) and interpreted in terms of competition between localization of
the U 5f states and the f-p hybridization. It is the spin-orbit interaction on
the chalcogen p states that plays an essential role in enlarging the strength
of the f-p hybridization in UTe, leading to an anomalous systematic trend in
the magnetic anisotropy.Comment: 4 pages, 5 figure
Observation of magnetic circular dichroism in Fe L_{2,3} x-ray-fluorescence spectra
We report experiments demonstrating circular dichroism in the x-ray-fluorescence spectra of magnetic systems, as predicted by a recent theory. The data, on the L_{2,3} edges of ferromagnetic iron, are compared with fully relativistic local spin density functional calculations, and the relationship between the dichroic spectra and the spin-resolved local density of occupied states is discussed
Electronic and Magnetic Structures of Sr2FeMoO6
We have investigated the electronic and magnetic structures of Sr2FeMoO6
employing site-specific direct probes, namely x-ray absorption spectroscopy
with linearly and circularly polarized photons. In contrast to some previous
suggestions, the results clearly establish that Fe is in the formal trivalent
state in this compound. With the help of circularly polarized light, it is
unambiguously shown that the moment at the Mo sites is below the limit of
detection (< 0.25mu_B), resolving a previous controversy. We also show that the
decrease of the observed moment in magnetization measurements from the
theoretically expected value is driven by the presence of mis-site disorder
between Fe and Mo sites.Comment: To appear in Physical Review Letter
Satellite holmium M-edge spectra from the magnetic phase via resonant x-ray scattering
Developing an expression of resonant x-ray scattering (RXS) amplitude which
is convenient for investigating the contributions from the higher rank tensor
on the basis of a localized electron picture, we analyze the RXS spectra from
the magnetic phases of Ho near the absorption edges. At the
edge in the uniform helical phase, the calculated spectra of the absorption
coefficient, the RXS intensities at the first and second satellite spots
capture the properties the experimental data possess, such as the spectral
shapes and the peak positions. This demonstrates the plausibility of the
adoption of the localized picture in this material and the effectiveness of the
spectral shape analysis. The latter point is markedly valuable since the
azimuthal angle dependence, which is one of the most useful informations RXS
can provides, is lacking in the experimental conditions. Then, by focusing on
the temperature dependence of the spectral shape at the second satellite spot,
we expect that the spectrum is the contribution of the pure rank two profile in
the uniform helical and the conical phases while that is dominated by the rank
one profile in the intermediate temperature phase, so-called spin slip phase.
The change of the spectral shape as a function of temperature indicates a
direct evidence of the change of magnetic structures undergoing. Furthermore,
we predict that the intensity, which is the same order observed at the second
satellite spot, is expected at the fourth satellite spot from the conical phase
in the electric dipolar transition.Comment: 24 pages, 5 figure
Rare earth contributions to the X-ray magnetic circular dichroism at the Co K edge in rare earth-cobalt compounds investigated by multiple-scattering calculations
The X-ray magnetic circular dichroism (XMCD) has been measured at the Co K
edge in Co-hcp and R-Co compounds (R=La, Tb, Dy). The structure of the
experimental XMCD spectra in the near-edge region has been observed to be
highly sensitive to the magnetic environment of the absorbing site.
Calculations of the XMCD have been carried out at the Co K edge in Co metal,
LaCo and TbCo within the multiple-scattering framework including the
spin-orbit coupling. In the three systems, the XMCD spectra in the near-edge
region are well reproduced. The possibility to separate and quantitatively
estimate the local effects from those due to the neighboring atoms in the XMCD
cross section makes possible a more physical understanding of the spectra. The
present results emphasize the major role played by the states of the Tb
ions in the XMCD spectrum at the Co K edge in the TbCo compound.Comment: 34 pages, revtex, 10 eps figures included with epsf, after referee
revie
Direct observation of electron doping in La0.7Ce0.3MnO3 using x-ray absorption spectroscopy
We report on a X-ray absorption spectroscopic (XAS) study on a thin film of
La0.7Ce0.3MnO3, a manganite which was previously only speculated to be an
electron doped system. The measurements clearly show that the cerium is in the
Ce(IV) valence state and that the manganese is present in a mixture of Mn2+ and
Mn3+ valence states. These data unambiguously demonstrate that La0.7Ce0.3MnO3
is an electron doped colossal magnetoresistive manganite, a finding that may
open up new opportunities both for device applications as well as for further
basic research towards a better modelling of the colossal magnetoresistance
phenomenon in these materials.Comment: 4 pages, 3 figures, revised versio
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