Jb Goedkoop

CIRCULARLY POLARIZATION LINE FILTERS IN THE SOFT-X-RAY RANGE

Abstract A feasibility study of the application of the recently discovered strong magnetic X-ray dichroism of rare earth materials to the production of circularly polarized X-rays is reported. A device is described that can be inserted downstream from a high resolution double beryl crystal monochromator. Calculations show that 45% transmission can be obtained with filters that yield 99% circular polarization in the energy range 950–1500 eV. Advantages of the proposed device are the low costs, the ease of installation and the high product of transmission × polarization.

Soft X-ray monochromatisation using a multilayer-single crystal combination

Abstract A method of monochromatising soft X-rays by using multilayers in combination with organic crystals is presented. An energy resolution of 0.1% has been achieved at ca. 800 eV. The combination can be used for high resolution studies in the energy range 500–800 eV, which is difficult to cover using either inorganic double crystals or grating monochromators.

Magnetic-Properties of Fe and Tb in Tbxfe1-X Amorphous Films Studied with Soft-X-Ray Circular and Linear Dichroism

Abstract We have used linearly and circularly polarized X-rays to determine the magnetic properties of several Tb x Fe 1− x amorphous films. Absorption measurements on the M 4.5 edges of Tb and the L 2.3 edges of Fe allowed us to obtain information about the size and direction of local magnetic moments. Our results confirm that linear dichorism in rare earth M 4.5 edges can give useful information about both crystal field and magnetic effects.

CHARACTERIZATION OF MULTILAYERS AS MONOCHROMATORS USING 200-900 EV SYNCHROTRON RADIATION

Various experiments on characterization of multilayers using synchrotron radiation in the region 200–900 eV are reported. Two Ni-C multilayer reflection coatings (d = 31 A) were used to construct a double “crystal” monochromator with a resolution EΔE ranging from ≈ 60 to ≈100 depending on energy. This monochromator has been used to record L2,3 absorption spectra of 3d-transition metals and the C, O and F K edges in solids. Strong structure has been found in the transmitted intensity of the multilayer monochromator near the absorption edges of the component elements of the coating. This structure can be explained only if the fine details of the refractive indices for the coating materials are taken into account. We also report on measurements on a multilayer coating with laterally graded g-spacing, which is a potential radiation resistent premonochromator.

X-ray dichroism of Dy overlayers on Ni(110)

Abstract Angle dependent X-ray absorption measurements of Dy on Ni(110) are presented, showing large dichroism effects. These effects were clearly observable, even in very thin layers (0.25 ML) and at room temperature, and indicate the potential of X-ray dichroism for studies of the magneto-crystalline field anisotropy at the surface. In contrast to measurements of spin polarization, MXD probes the total moment of the ions, including the orbital moment. The interpretation of the results in terms of a magnetized free-ion model is discussed.

Reflection Extended X-Ray Absorption Fine-Structure Measurements on Ni/C and Nixsiy/C Multilayered Reflection Coatings

A new method is described to measure bond lengths in the interface between thin layers, by using multilayered reflection coatings both as a dispersive element in an x‐ray beam, and as an object of measurement. Extended x‐ray absorption fine‐structure (EXAFS) oscillations can be observed in the reflected spectrum. From multilayered Ni/C and NixSiy/C reflection coatings mounted in a double‐crystal monochromator we determined, from these oscillations above the Ni LII,III edge, bond lengths equal to 1.8, 2.1, and 2.3 A, which can be assigned to Ni–C, Ni–Si, and Ni–Ni, respectively. NixSiy/C coatings deposited in a 10−6 Torr H2 atmosphere show better resolution than those without. The difference is ascribed to H2 preventing the formation of silicides and the diffusion of the Ni into the carbon; this results in more amorphous layers. A new and simple method is described for obtaining, in the EXAFS analysis, a high‐resolution radial distribution function (RDF) from a small k‐vector space chi function. This metho...