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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4627-4629 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The electronic structure of PtMnSb has been studied by means of the linear muffin-tin-orbital method of band-structure calculation. In agreement with earlier investigations a so-called half-metallic behavior has been found. Until now, this exotic feature of the band structure of PtMnSb, which is made responsible by some authors for its high Kerr rotation, could not clearly be confirmed by experiment. Using the Korringa–Kohn–Rostoker band-structure technique it could be shown that lattice imperfections, which can never be completely suppressed in this system, have a dramatic impact on the spin polarization in the vicinity of the Fermi level. This explains why photoemission experiments could find only a degree of photoelectron polarization at the threshold noticeable below the ideal value of 100%. To get further insight into these problems, x-ray-absorption measurements using circularly polarized radiation have been performed at the L2,3 edges of Pt, the K edge of Mn, and the L1 edge of Sb. The results of these experiments, which give in a component-resolved way a rather direct access to the spin polarization for the unoccupied part of the conduction band, are found in reasonable agreement with theoretical data.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Circular magnetic x-ray dichroism (CMXD) was observed at the Pt and Ir L2,3 edges in the multilayered structures 25⋅(4 A(ring) Co+30 A(ring) Pt) and 25⋅(4 A(ring) Co+11 A(ring) Pt+8 A(ring) Ir+11 A(ring) Pt). The samples were prepared by sputtering and show a large perpendicular anisotropy. The magnetic absorption at the Pt and Ir L2,3 edges was measured in an external magnetic field of 0.15 T perpendicular to the surface. The results indicate a significant spin polarization of the Pt and Ir layers. By comparison with the corresponding CMXD signals of Pt and Ir impurities in a ferromagnetic iron host we estimated the local spin and orbital moments. The results show that the innermost three monolayers in both systems couple ferromagnetically to the Co layers with an average magnetic moment of about 0.01 μB.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5347-5347 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Systematic studies of the magnetic or spin-dependent EXAFS (SPEXAFS) were performed at the L2/3 edges of Eu3Fe5O12, Gd and Tb metal and the alloy Ho20Gd80. The magnetic absorption exhibits distinct EXAFS structure, more pronounced than the nonmagnetic EXAFS. The Fourier transform of the Eu L2/3-edges SPEXAFS spectra, which are measured with an accuracy of less than 5×10−5, show a complete disappearance of the oxygen peak. This allows an identification of the positions of the magnetic neighbors for a significantly longer range as it is possible by using the conventional EXAFS profile. Studies of the alloy Ho20Gd80 at the L2/3 edges of both components, which show no significant differences in the polarization averaged EXAFS, indicate an essential influence of the spin structure at the absorbing atom on the magnetic EXAFS spectrum. At the L3 edge of Gd and Tb metal (both of hcp structure) we found similar structures in the conventional as well as in the magnetic EXAFS. The data are interpreted in terms of the sensibility of the SPEXAFS on the angular momentum of the absorbing and neighboring atoms.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6910-6912 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The local magnetic structure of TbFe multilayers with various layer thicknesses of Tb (26 A(ring)) and Fe (10, 20, 30 and 35 A(ring)) has been investigated by circular magnetic x-ray dichroism (CMXD) studies. From the dichroic signal at the L3 edge both the local magnetic Tb moment and the anisotropic behavior of the Tb compound could be deduced. The magnetic spectra at the Tb L2 edge and the Fe K edge, which are known to be sensitive to the local chemical environment, have been used to obtain information on the binding characters of the magnetized atoms in the various TbFe compositions. Significant deviations of the CMXD spectra compared to the corresponding spectra in the pure Fe and Tb metals have been observed. This indicates significant contributions to the magnetism from an interface region, whose chemical structure resembles strongly those of the intermetallic TbFe2 compounds.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Spin-dependent absorption spectroscopy or circular magnetic x-ray dichroism studies at the L2,3 edges of 5d atoms in ferromagnetic hosts have been used to investigate the spin-density distribution of the empty d-projected states and thus the local magnetic moment of the absorbing 5d atoms. This method was applied to study the average polarization of the Pt atom in Co/Pt multilayers with different modulation lengths. The spin-dependent absorption profiles for vapor-deposited [25(4 A(ring) Co+x A(ring) Pt), x=9, 16, 23, 30, 40] multilayers indicate a significant average Pt polarization decreasing with the layer thickness. The experimental results are discussed in comparison with spin-polarized relativistic band-structure calculations (linear muffin-tin-orbital calculations).
    Materialart: Digitale Medien
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  • 6
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have performed systematic investigations of the circular magnetic x-ray dichroism, i.e., the spin-dependent absorption of circularly polarized x rays at the L2,3 edges of the 4f elements in the compound (RE)2Co17. In all systems significant CMXD signals with relative large amplitudes of some percent have been found. It is expected, that the spin-dependent absorption profile reflects the spin-density of d-like unoccupied states at the Fermi level and thus contains information on the orientation of the 4f moment. The ratio of the CMXD signal at the L2 and L3 edges depends strongly on the angular momentum of the 4f core and indicates in case of Ce2Co17, that the 4f electrons are of itinerant character with almost quenched angular momentum, as theoretically expected for similar Ce systems.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6147-6149 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The spectroscopy of spin-dependent absorption using circularly polarized synchrotron radiation is a new method to study the magnetic structure of multicomponent systems. We demonstrate for substitutional 5d transition-metal impurities in an iron host that from L2,3 spin-dependent absorption signal information on the local magnetic moment, carried by the d electrons of the absorbing atom, can be deduced. The experimentally determined local magnetic moments of the 5d impurities in Fe are in good agreement with the theoretical results based on the spin-polarized relativistic Korringa–Kohn–Rostoker–Green function method of band-structure calculation. The presented data are−to our knowledge−the first experimental proof of the change from antiferro- to ferromagnetic coupling between Os and Ir, which has been predicted by the above-mentioned calculations.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4456-4458 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The spin dependence of L2,3 absorption in 5d atoms oriented in a ferromagnetic matrix contains information on the spin density of the empty d-projected states of the absorbing atom. Spin-dependent absorption spectroscopy using circularly polarized synchrotron radiation was applied to study the polarization of the Pt atoms in the binary alloy Co50Pt50 and Pt/Co layered structures, which are promising candidates for magneto-optical recording. The spin-dependent absorption signals for vapor-deposited 250(4 A(ring) Co+18 A(ring) Pt) and 250(6 A(ring) Co+18 A(ring) Pt) multilayers indicate a ferromagnetic coupling on Pt and Co atoms with a significant Pt polarization. This is reduced on average by about 60% with respect to the Pt polarization in the Co50Pt50 alloy. The experimental results are discussed on the basis of spin-polarized band-structure calculations.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5346-5346 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The interference of charge and magnetic scattering from ferromagnetic targets leads in case of circularly polarized x rays to a relative difference (flipping ratio) of the Bragg peak intensity in the order of 10−3, when the magnetization aligned in the scattering plane is reversed (spin-dependent scattering). We have measured the spin-dependent scattering in Fe, Gd, and Tb polycrystalline metallic foils using circularly polarized synchrotron radiation. From the data, magnetic form factors have been deduced. As demonstrated for Gd and Tb, from the flipping ratios the orbital and spin contribution can be directly separated by varying the angle between the scattering vector and the sample magnetization. Spin-dependent resonance scattering has been studied at the K edge of a Ni single crystal. A significant enhancement of the magnetic scattering amplitude compared to the magnetic resonance scattering of linearly polarized light and sample magnetization perpendicular to the scattering plane has been observed. A strongly increased nonresonant magnetic scattering with opposite sign compared to the resonant magnetic effects is observed in the preedge energy region below −10 eV with respect to the K-absorption onset. The applicability of magnetic scattering using circularly polarized synchrotron radiation for the investigation of ferromagnetic media especially in view of its complementarity to neutron studies is discussed.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The method of spin-dependent absorption has been used to examine the temperature dependence of the circular magnetic x-ray dichroism (CMXD) of the (disordered) Invar alloy fcc Fe72Pt28. At the Fe K edge the difference of the transmission for the reversed magnetization direction was determined with an accuracy of 10−5. By comparing the dichroic effects at 110 and at 410 K evidence was found for a temperature-dependent change of the magnetic absorption profile different from the pure amplitude reduction due to the reduced magnetization. It indicates a change of the spin splitting in the low-lying unoccupied p states. The polarization-averaged absorption spectrum shows also a small variation between 4 and 11 eV above the threshold indicating that the p-like electron density drops when the sample is heated. The experimental CMXD profiles are compared with spin-polarized band-structure calculations for ordered Fe3Pt and discussed within the frame of the model of high-spin–low-spin transitions in the Invar regime.
    Materialart: Digitale Medien
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