Fe 2p absorption in magnetic oxides: Quantifying angular-dependent saturation effects

Gota, S.; Gautier-Soyer, M.; Sacchi, M.

doi:10.1103/physrevb.62.4187

Cited by 110 publications

(110 citation statements)

References 20 publications

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“…However, recent communications with that group have now revealed that there was an error in the wavelength scale in that paper (J. P. Crocombette 2000, private communication;M. Gautier-Soyer et al 2001, in preparation;Gota, Gautier-Soyer, & Maurizio 2000) and that the deepest resonance complex for iron oxides is instead centered at 17.46 Å . While closer, this revised value still differs significantly from the wavelength of the observed edgelike feature in the MCG À6-30-15 spectrum, by more than the uncertainty attributable to the RGS instrument.…”

Section: Absorption By Dust Particlesmentioning

confidence: 99%

Can a Dusty Warm Absorber Model Reproduce the Soft X‐Ray Spectra of MCG −6‐30‐15 and Markarian 766?

Šako¹,

Kahn²,

Branduardi‐Raymont³

et al. 2003

ApJ

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XMM-Newton RGS spectra of MCG À6-30-15 and Mrk 766 exhibit complex discrete structure, which was interpreted in a paper by Branduardi-Raymont and coworkers as evidence for the existence of relativistically broadened Ly emission from carbon, nitrogen, and oxygen, produced in the innermost regions of an accretion disk around a Kerr black hole. This suggestion was subsequently criticized in a paper by Lee and coworkers, who argued that for MCG À6-30-15, the Chandra HETG spectrum, which is partially overlapping the RGS in spectral coverage, is adequately fitted by a dusty warm absorber model, with no relativistic line emission. We present a reanalysis of the original RGS data sets in terms of the model by Lee and coworkers. Specifically, we show that (1) the explicit model given by Lee and coworkers differs markedly from the RGS data, especially at longer wavelengths, beyond the region sampled by the HETG; (2) generalizations of the Lee and coworkers model, with all parameters left free, do provide qualitatively better fits to the RGS data, but are still incompatible with the detailed spectral structure; (3) the ionized oxygen absorption-line equivalent widths are well measured with the RGS for both sources, and place very tight constraints on both the column densities and turbulent velocity widths of O vii and O viii. The derived column densities are well below those posited by Lee and coworkers and are insufficient to play any role in explaining the observed edge-like feature near 17.5 Å ; (4) the lack of a significant neutral oxygen edge near 23 Å places very strong limits on any possible contribution of absorption to the observed structure by dust embedded in a warm medium; and (5) the original relativistic line model with warm absorption proposed by BranduardiRaymont and coworkers provides a superior fit to the RGS data, both in the overall shape of the spectrum and in the discrete absorption lines. We also discuss a possible theoretical interpretation for the putative relativistic Ly line emission in terms of the photoionized surface layers of the inner regions of an accretion disk. While there are still a number of outstanding theoretical questions about the viability of such a model, it is interesting to note that simple estimates of key parameters are roughly compatible with those derived from the observed spectra.

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Section: Absorption By Dust Particlesmentioning

confidence: 99%

Can a Dusty Warm Absorber Model Reproduce the Soft X‐Ray Spectra of MCG −6‐30‐15 and Markarian 766?

Šako¹,

Kahn²,

Branduardi‐Raymont³

et al. 2003

ApJ

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“…Because of the different electronic structure between metals and insulators, in particular the gap in the density of states near the Fermi level in the latter that will influence the secondary electron cascade, insulators are expected to have a larger electron sampling depth. Little literature is available on this topic [9,10,11,12]. Gota et al [11] found an unexpectedly high value for the sampling depth of the iron magnetic oxide Fe 3 O 4 of 4.5 nm, in comparison to the one known for metallic Fe in the range 1.7 -2.2 nm, while d ≈ 2nm was found both in Ta 2 O 5 at the O K-3 edge [9] and in LaFeO 3 at the Fe L 2,3 edge [12].…”

Section: Introductionmentioning

confidence: 99%

“…Little literature is available on this topic [9,10,11,12]. Gota et al [11] found an unexpectedly high value for the sampling depth of the iron magnetic oxide Fe 3 O 4 of 4.5 nm, in comparison to the one known for metallic Fe in the range 1.7 -2.2 nm, while d ≈ 2nm was found both in Ta 2 O 5 at the O K-3 edge [9] and in LaFeO 3 at the Fe L 2,3 edge [12]. Recently, transition-metal oxides with the perovskite structure and their interfaces have been intensely investigated, especially using XAS techniques to probe their interfaces [13,14] because of their potential application in spintronic or superconducting devices.…”

Section: Introductionmentioning

confidence: 99%

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Electron sampling depth and saturation effects in perovskite films investigated by soft x-ray absorption spectroscopy

et al. 2014

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Knowledge of the electron sampling depth and related saturation effects is important for quantitative analysis of X-ray absorption spectroscopy data, yet for oxides with the perovskite structure no quantitative values are so far available. Here we study absorption saturation in films of two of the moststudied perovskites, La 0.7 Ca 0.3 MnO 3 (LCMO) and YBa 2 Cu 3 O 7 (YBCO), at the L 2,3 edge of Mn and Cu, respectively. By measuring the electron-yield intensity as a function of photon incidence angle and film thickness, the sampling depth d, photon attenuation length λ and the ratio λ/d have been independently determined between 50 and 300 K. The extracted sampling depth d LCMO ≈ 3 nm for LCMO at high temperatures in its polaronic insulator state (150 -300 K) is not much larger than values reported for pure transition metals (d Co or Ni ≈ 2 -2.5 nm) at room temperature, but is smaller than d YBCO ≈ 3.9 nm for metallic YBCO that is in turn smaller than the value reported for Fe 3 O 4 (d Fe3O4 ≈ 4.5 nm). The measured d LCMO increases to 4.5 nm when LCMO is in the metallic state at low temperatures. These results indicate that a universal rule of thumb for the sampling depth in oxides cannot be assumed, and that it can be measurably influenced by electronic phase transitions that derive from strong correlations.

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“…The latter effect is attributed to the difference between surface-and bulk-sensitive measurements due to the x-ray absorption length in this energy range ͑ϳ20 nm͒. 22 Given the XAS surface sensitivity, XFMR can be applied to samples with thickness down to a few tens of nm without considerable loss of signal. This makes it straightforward to extend XFMR to metallic samples where the skineffect limits the penetration of microwave radiation.…”

mentioning

confidence: 99%

X-ray ferromagnetic resonance spectroscopy

Boero

Rusponi

Benčok

et al. 2005

Applied Physics Letters

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We present a method to measure continuous-wave ferromagnetic resonance ͑FMR͒ spectra based on the core-level absorption of circularly polarized x rays. The technique is demonstrated by using a monochromatic x-ray beam incident on an yttrium-iron-garnet sample excited by a microwave field at 2.47 GHz. FMR spectra are obtained by monitoring the x-ray absorption intensity at the photon energy corresponding to the maximum of the magnetic circular dichroism effect at the iron L 2,3 edges as a function of applied magnetic field. The x-ray FMR signal is shown to be energy dependent, which makes the technique element sensitive and opens up new possibilities to perform element-resolved FMR in magnetic alloys and multilayers.

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Fe 2p absorption in magnetic oxides: Quantifying angular-dependent saturation effects

Cited by 110 publications

References 20 publications

Can a Dusty Warm Absorber Model Reproduce the Soft X‐Ray Spectra of MCG −6‐30‐15 and Markarian 766?

Can a Dusty Warm Absorber Model Reproduce the Soft X‐Ray Spectra of MCG −6‐30‐15 and Markarian 766?

Electron sampling depth and saturation effects in perovskite films investigated by soft x-ray absorption spectroscopy

X-ray ferromagnetic resonance spectroscopy

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