X-ray resonant magnetic scattering: polarization dependence in the non-spherical case

Mirone, Alessandro; Bouchenoire, Laurence; Brown, S. D.

doi:10.1107/s0108767307023720

Cited by 5 publications

(6 citation statements)

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“…1 and 2 cannot be attributed to E2 scattering. Also, E1-E2 scattering can be ruled out as this can only occur at satellites around odd values of l. 6 We therefore conclude that the experimentally observed π →σ scattering is predominantly of E1 origin. The insets of Figs.…”

mentioning

confidence: 60%

“…4 This model was later rewritten explicitly in terms of the angular dependences 5 with the approximation of spherical symmetry and more recently to include the noncentrosymmetric case applicable to all of the hexagonal close-packed heavy rare earths. 6 In early x-ray spectroscopic studies, 2,3,[7][8][9][10][11][12] the lower-energy peaks were generally interpreted as E2 and the higher energy ones as E1, due to the predicted polarization and angular dependences of the observed features.…”

mentioning

confidence: 99%

“…5,6 In Eq. (2),theE2terms multiplied by cos2θ will be negligible for the scattering angles involved here, and the final first-order term will dominate, which is reduced by a factor of 3/8 compared to the E1 amplitude in Eq.…”

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confidence: 99%

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4f/5dhybridization in the heavy rare earth elements Er and Tm

et al. 2013

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We present experimental data and first-principles calculations of the x-ray resonant magnetic scattering (XRMS) line shapes of Er and Tm metals. Band structure calculations are presented that illustrate the existence of 4f/5d hybridization of unoccupied electron levels. This leads to spin and orbital features in the XRMS spectra that are not representative of the 5d occupied moments. General trends through the heavy rare earth series are discussed with reference to previous work.

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confidence: 60%

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4f/5dhybridization in the heavy rare earth elements Er and Tm

et al. 2013

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“…The (0 0 2n±τ) reflections were analyzed in the theoretical framework of a spherical magnetic atom [23,24]. Only the final equations are presented in this section.…”

Section: Total X-ray Scattering Cross-section (Tmcs)mentioning

confidence: 99%

“…In that respect, we show in this article that it is possible to recover the XMCD spectrum by using the imaginary part of the resonant scattering factors and thus to extract the energy dependence of both E1 and E2 contributions that compose it. Knowing the exact position of the pure electric E1 and E2 transitions can also aid understanding of new phenomena that originate from E1-E2 scattering in non-centrosymmetric systems [24] (to be addressed in the future).…”

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E1 and E2 contributions to the L₃resonance line shape in antiferromagnetic holmium

Bouchenoire¹,

Mirone²,

Brown³

et al. 2009

New J. Phys.

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A detailed study of the angular, energy and polarization dependences of the electric dipolar (E1: 2p→5d) and quadrupolar (E2: 2p→4f) contributions to the x-ray scattering crosssection is presented for holmium in its basal plane spiral antiferromagnetic phase at the L 3 edge. The corresponding E1 and E2 scattering factors have been extracted from fits to the experimental energy line shapes taking into account for the first time a split dipole resonance. Using the imaginary part of the resonant scattering factors to retrieve the XMCD spectrum, we find qualitative agreement with the dichroic spectrum measured in transmission through a holmium foil. Derivation of the TMCS for magnetic moments lying in the a-b plane Appendix B. Fitting procedure References IntroductionThe magnetism of rare-earth (RE) materials is of huge technological importance. Among other key applications, REs can be found in high-performance permanent magnets [1-3], as dopants in optical data storage devices [4,5] and in high speed magnetoelectronic devices [6,7]. An improved understanding of the electronic and magnetic properties of RE metals, including their interactions with other atoms in compounds and alloys, is crucial for developing future technologies. To this end, synchrotron x-rays are proving to be an important probe of RE magnetism [8,9]. Such experiments are carried out close to an atomic absorption edge by studying either absorptionnamely, x-ray magnetic dichroism, either with circularly (i.e. XMCD) or linearly (i.e. XMLD) polarized photons -or scattering, where scattering can be performed either in the elastic or inelastic regime, namely by x-ray resonant magnetic scattering (XRMS) or resonant inelastic x-ray scattering (RIXS) respectively.Controversy, however, surrounds the identification of E1 (dipolar) and E2 (quadrupolar) features in energy line shapes measured across the RE L 2,3 absorption edges in XRMS [10-12], XMCD [13][14][15][16] and RIXS [17,18]. The observation of a pre-edge peak (where the position of the "absorption edge″ itself is normally defined as the first inflection point of an absorption curve) has generally been interpreted as arising, purely, from E2 processes, whereas the higher energy peak has been attributed to E1 excitations. However, deviations from this understanding have appeared in the literature: in an XMCD study at the Yb L 3 absorption edge, where a dichroic signal observed at the edge was interpreted to be E2 in origin, while a lower energy feature was assigned to be E1 [19]; in an XRMS study at the Tb L 2,3 edges where (again) the low energy peak was interpreted to be E1 and the high energy peak to be E2 [20]. More importantly, a recent combined experiment and theory investigation of charge-magnetic x-ray resonant interference scattering (XRIS) -a technique which is a "subset" of elastic resonant scattering (i.e. XRMS) -carried out by Brown et al [21,22], studying ferro-and ferri-magnetic phases of the hexagonal close-packed, heavy RE metals (moments along the c-axis), has challenged the general i...

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Thermodynamic Characterization of the DmsD Binding Site for the DmsA Twin-Arginine Motif

Winstone

Turner

2015

Biochemistry

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The system specific chaperone DmsD interacts with the twin-arginine leader peptide of its substrate, DmsA, allowing for proper folding and assembly of the DmsA catalytic subunit of dimethyl sulfoxide reductase prior to translocation by the twin-arginine translocase. DmsD residues important for binding the complete 45-amino acid sequence of the DmsA leader (DmsAL) peptide were previously identified and found to cluster in a pocket of the DmsD structure. In this study, we have utilized isothermal titration calorimetry (ITC) to determine the dissociation constant and thermodynamic parameters of 15 single-substitution DmsD variant proteins and a synthetic DmsAL peptide consisting of 27 amino acids (DmsAL₁₅₋₄₁). The stoichiometry values were determined via ITC, and the multimeric compositions of the DmsD variants in the absence and presence of peptide were characterized via size exclusion chromatography and native polyacrylamide gel electrophoresis. An up to 4-fold change in affinity was observed for DmsD variant proteins relative to that of wild-type DmsD, and variation of the entropic contribution to binding divided the binding site into two clusters: residues with either more or less favorable entropy. Substitution of hydrophobic residues along one helix face (helix 5) or prolines found on adjacent loops caused reduced binding affinity because of the increased entropic cost, which suggests that the twin-arginine motif of the DmsAL peptide binds to a preformed site on DmsD. Most DmsD variants were more than 90% monomeric in solution and bound a single peptide per protein molecule. The DmsD variant with the largest dimer population showed increased affinity and induced the formation of tetramers in the presence of peptide, suggesting that dimeric DmsD or an alternatively folded form of DmsD may play an as yet undefined role in binding.

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X-ray resonant magnetic scattering: polarization dependence in the non-spherical case

Cited by 5 publications

References 14 publications

4f/5dhybridization in the heavy rare earth elements Er and Tm

4f/5dhybridization in the heavy rare earth elements Er and Tm

E1 and E2 contributions to the L₃resonance line shape in antiferromagnetic holmium

Thermodynamic Characterization of the DmsD Binding Site for the DmsA Twin-Arginine Motif

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X-ray resonant magnetic scattering: polarization dependence in the non-spherical case

Cited by 5 publications

References 14 publications

4f/5dhybridization in the heavy rare earth elements Er and Tm

4f/5dhybridization in the heavy rare earth elements Er and Tm

E1 and E2 contributions to the L3resonance line shape in antiferromagnetic holmium

Thermodynamic Characterization of the DmsD Binding Site for the DmsA Twin-Arginine Motif

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E1 and E2 contributions to the L₃resonance line shape in antiferromagnetic holmium