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61.
62.
L. Braicovich F. Borgatti A. Tagliaferri G. Ghiringhelli N.B. Brookes P. Ferriani C.M. Bertoni 《Applied Physics A: Materials Science & Processing》2001,73(6):679-686
We discuss the application of resonant inelastic X-ray scattering to the study of magnetic systems in the soft X-ray range.
To this end we distinguish two broad areas. In the first the layout of the experiment is such that the absorption magnetic
circular dichroism (MCD) is not zero. In the second the magnetisation is perpendicular to the incident helical beam so that
the absorption MCD is zero. In the first area we summarise published results on Fe-Co alloys and we present new data on Mn
impurities in Ni together with calculations. In the second area we summarise published results on Ni in Ni-ferrite with final
3s shell excitation and we present new results on Co-metal and Co in Co-ferrite measured with a new approach. This is based
on the incident energy dependence of the integral of the Raman spectrum in inner shell excitation (integrated resonant Raman
scattering). The potentialities and the limitations of the above methods are critically presented.
Received: 23 May 2001 / Accepted: 4 July 2001 / Published online: 5 October 2001 相似文献
63.
Heaton RJ Brookes R Madden PA Salanne M Simon C Turq P 《The journal of physical chemistry. B》2006,110(23):11454-11460
The construction of an interaction potential for BeF2 and its mixtures with LiF on a purely first-principles basis is described. The quality of the representation of the forces on the ions obtained from ab initio electronic structure calculations by various potentials, which include many-body interaction effects to different extents, are considered. The predictions of the properties of pure BeF2 obtained in simulations with a polarizable potential are then compared with experimental values. In the subsequent paper, a more extensive comparison of the predicted properties of LiF-BeF2 mixtures with experiment is considered. 相似文献
64.
P. Thakur J. C. Cezar N. B. Brookes R. J. Choudhary D. M. Phase K. H. Chae Ravi Kumar 《Hyperfine Interactions》2010,197(1-3):95-100
The electronic and magnetic properties of well characterized Mo1???xFexO2 (x = 0–0.5) thin films that show ferromagnetism at room temperature (RT) have been investigated by the means of near edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) experiments at the O K-, Fe L-, and Mo M-edges. The NEXAFS spectra at O K- and Mo M3,2 -edges show a strong hybridization of O 2p-4d Mo orbitals, and Mo ions change their symmetry with the substitution of Fe ions into MoO2 matrix. The Fe 2p NEXAFS/XMCD spectra exhibit multiple absorption peaks and an appreciable XMCD signal that persists even at RT. These results demonstrate that Fe is in a mixed valence state of Fe2?+?–Fe3?+?, substituting at the Mo site and that the Fe2?+?/3?+? ions are ferromagnetically polarized. 相似文献
65.
M. Sicot P. Turban S. Andrieu A. Tagliaferri C. De Nadai N.B. Brookes F. Bertran F. Fortuna 《Journal of magnetism and magnetic materials》2006
The half-metallic NiMnSb alloy was tested as a possible fully polarized electrode in a magnetic tunnel junction. For this purpose, epitaxial NiMnSb(0 0 1) and NiMnSb/MgO(0 0 1) systems were grown by molecular beam epitaxy. Spin-polarized photoemission experiments using the synchrotron radiation at the ESRF were performed on both the uncovered NiMnSb(0 0 1) surface and on the NiMnSb/MgO(0 0 1) interface. Starting from a NiMnSb(0 0 1) uncovered surface presenting at room temperature a 40% polarization at the Fermi level measured in the whole Brillouin zone, this polarization was observed to dramatically decrease when a MgO(0 0 1) epitaxial barrier was grown on top of it. On the other hand, the X-ray absorption experiments clearly show some oxidization of Mn after growing the MgO layer. This behavior was confirmed by testing the electronic and chemical properties of a unique atomic plane of Mn grown on a Fe buffer layer, before and after growing a MgO layer on top of it. 相似文献
66.
67.
Bruno FY Garcia-Barriocanal J Varela M Nemes NM Thakur P Cezar JC Brookes NB Rivera-Calzada A Garcia-Hernandez M Leon C Okamoto S Pennycook SJ Santamaria J 《Physical review letters》2011,106(14):147205
We report on the magnetic coupling of La0.7Sr0.3MnO3 layers through SrTiO3 spacers in La0.7Sr0.3MnO3/SrTiO3 epitaxial heterostructures. Combined aberration-corrected microscopy and electron-energy-loss spectroscopy evidence charge transfer to the empty conduction band of the titanate. Ti d electrons interact via superexchange with Mn, giving rise to a Ti magnetic moment as demonstrated by x-ray magnetic circular dichroism. This induced magnetic moment in the SrTiO3 controls the bulk magnetic and transport properties of the superlattices when the titanate layer thickness is below 1 nm. 相似文献
68.
The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. A simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure for the Born cross-sections that employs the Elwert–Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. We also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations. 相似文献
69.
Tebano A Aruta C Sanna S Medaglia PG Balestrino G Sidorenko AA De Renzi R Ghiringhelli G Braicovich L Bisogni V Brookes NB 《Physical review letters》2008,100(13):137401
Linear dichroism (LD) in x-ray absorption, diffraction, transport, and magnetization measurements on thin La(0.7)Sr(0.3)MnO(3) films grown on different substrates, allow identification of a peculiar interface effect, related just to the presence of the interface. We report the LD signature of preferential 3d-e(g)(3z(2)-r(2)) occupation at the interface, suppressing the double exchange mechanism. This surface orbital reconstruction is opposite to that favored by residual strain and is independent of dipolar fields, the chemical nature of the substrate and the presence of capping layers. 相似文献
70.