Keiji Fukui

Theory of Magnetic Circular Dichroism of the Ce L2,3 X-ray Absorption Spectra in Mixed Valence Vompound CeFe2

Magnetic circular dichroism (MCD) of x-ray absorption spectroscopy (XAS) at Ce L 2,3 edges in the typical mixed valence compound CeFe 2 is theoretically studied by using the impurity Anderson model combined with a cluster approach. It is found that the energy-dependent polarization of Ce 5 d states due to mixing with spin-polarized Fe 3 d states is indispensable for explaining the spectra. Our calculations reproduce well the two-peak structure observed in XAS and MCD experiments, especially their energy position, spectral width and energy separation of the two peaks. For a detailed analysis of these, the Coulomb interactions - U d c (between a 5 d electron and a core hole) and U f d (between a 4 f electron and a 5 d electron) play a special role.

Magnetic Circular Dichroism of Resonant X-Ray Emission Spectroscopy in Longitudinal and Transverse Geometries

Theoretical calculations and experimental measurements are performed for magnetic circular dichroism in resonant X-ray emission spectroscopy (MCD-RXES) in Gd 3+ systems. It is shown that when the i...

Magnetic Circular Dichroism of Resonant X-Ray Emission Spectroscopy in the Transverse Geometry

We perform theoretical calculations and experimental measurements for magnetic circular dichroism in resonant X-ray emission spectroscopy (MCD-RXES) in Gd 3+ systems. A general expression of MCD-RXES is obtained theoretically for arbitrary directions of incident and emitted X-rays with an atomic model. It is shown that when the incident X-ray is perpendicular to the magnetization of the sample the MCD-RXES originates from the quantum mechanical interference between the excitation and decay processes. The behavior of MCD-RXES calculated for the 2 p →5 d excitation and 3 d →2 p radiative decay in Gd 3+ is in good agreement with that measured experimentally for a Gd 33 Co 67 amorphous alloy.

X-ray magnetic circular dichroism at rare-earth L 2 , 3 edges in R 2 Fe 14 B compounds ( R = 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.

Cluster Model Calculation for X-Ray Magnetic Circular Dichroism at Rare-Earth (R) L2,3 Absorption Edges in R2Fe14B

X-ray magnetic circular dichroism (MCD) at the L 2,3 absorption edges for the entire series of rare-earth (RE) elements in R 2 Fe 14 B ( R =RE) is studied based on a cluster model including 10 RE and 16 Fe atoms. The cluster model takes into account band effects of RE 5 d states, to which the electric dipole transition occurs from the core 2 p states, as well as spin polarization of the 5 d states due to the interatomic hybridization with the spin polarized Fe 3 d states. We also take into account spin and orbital polarization of the 5 d states due to the 5 d –4 f intra-atomic exchange interaction, and the 2 p to 4 f quadrupole transition. The calculated results are in satisfactory agreement with experimental ones, suggesting that the cluster model calculation provides a new method to calculate quantitatively MCD spectra of RE systems with complicated atomic arrangements.

Magnetic circular dichroism of resonant X-ray emission spectra by electric quadrupole excitation

We give a theoretical prediction for the angle dependence of the magnetic circular dichroism in resonant X-ray emission spectroscopy (MCD-RXES) by the electric quadrupole excitation. After general ...

Magnetic circular dichroism of resonant X-ray emission spectra at L edges of rare-earth compounds

We study the resonant x-ray emission spectroscopy (RXES) and the magnetic circular dichroism (MCD) at the L2,3 absorption edges of rare-earth elements, especially gadolinium ion. To this end, an atomic model is adopted and the multiplet coupling effect is taken into account. Using the formula of the coherent second order optical process which consists of the excitation process from the 2p core state to the empty 5d state and of the radiative decay from the 3d core state to the 2p core hole, we calculate RXES-MCD spectra. By inspection, we have confirmed that the enhancement of the 2p-5d dipole matrix element proposed for MCD of x-ray absorption spectroscopy. In addition, characteristic features of the spectra observed in gadolinium metallic compounds are reproduced by our calculations.

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.

X-ray magnetic circular dichroism at rare-earthL2,3edges inR2Fe14Bcompounds(R=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.

X-ray magnetic circular dichroism at rare-earth (formula presented) edges in (formula presented) compounds (formula presented) 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.