Résumé des résultats (Abstract)
(Anglais)
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New optical elements for the broad-band polarization detector have been produced at PSI and characterized at BESSY II. Cr/C and V/Ni multilayers were designed as phase shifters in transmission and as analysers in reflection. The V/Ni multilayers showed a phase shift |D| = 7.6° at 512 eV and a reflectance ratio for linearly s- and p-polarized light RS/RP > 1000 for photon energies in the range 507-512 eV. For Cr/C multilayers a phase shift |D| = 21° was found at 577 eV and RS =20%, RS/RP = 1400 at 512 eV [1,2]. The values show that these components are suitable for polarization analysis at the mentioned energies. Analysers for higher photon energies were produced in the form of laterally graded W/Si multilayers. In addition, the reflectance of an YBCO layer, epitaxially grown at EPFL, was measured at BESSY. At 750 eV, RS =3.2% and RS/RP = 3500 was found; close to the Ba M5 edge, RS reached a maximum of 10% at 782 eV, whereas RS/RP dropped to 200.
We used the sensitivity of polarized soft X-rays to the magnetization of resonance atoms at the L3-edges of 3d metals to study the exchange coupling in a 10 nm Fe/ 5 nm NiO/ 10 nm Co trilayer. This trilayer of type soft ferromagnet (F) /antiferromagnet (AF)/ hard F served as a model system of a spin-valve device. The resonant magnetic reflectivity of p-linearly polarized X-rays revealed the presence of oxidized states of Fe, Co in addition to the metallic ones and the existence of an excess moment of the oxidized Ni. This implies significant mixing at the F/AF interfaces, which, in turn, affects the magnetic behaviour of each layer. We studied the magnetic reversal of metallic and oxidized states of Fe, Co and Ni and the influence of the cooling field on the exchange coupling [3,4].
References
(A complete list of publications and presentations at conferences for the reporting period is given in the report for the EU commission.)
[1] H. Grimmer, Optical Components for polarization analysis at the vanadium L3-edge and the carbon K-edge, Oral contribution to the workshop 'Resonant Soft X-Ray Scattering in Condensed Matter Physics', Villigen, Switzerland, March 29-30, 2001.
[2] H. Grimmer, O. Zaharko, M. Horisberger, H.-Ch. Mertins, F. Schäfers, Optical Components for polarization analysis at the vanadium L3-edge and the carbon K-edge, Accepted for publication in Surface Review and Letters.
[3] O. Zaharko, Domain wall formation in Fe/NiO/Co exchange coupled film studied by soft x-ray resonant magnetic scattering, Oral contribution to the workshop 'Resonant Soft X-Ray Scattering in Condensed Matter Physics', Villigen, Switzerland, March 29-30, 2001.
[4] O. Zaharko, Exchange coupling in Fe/NiO/Co film studied by soft x-ray resonant magnetic scattering, Oral contribution to the 4th International Symposium on Metallic Multilayers, Aachen, Germany, June 24-29, 2001.
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