[en] The magnetization of a thin Fe film epitaxially grown on GaAs(0 0 1)-4x6 was studied at different depths from the metal/semiconductor interface using a single layer of Fe_0.5Co_0.5 as a marker layer through a double-wedge Fe film. By measuring the X-ray magnetic circular dichroism spectroscopy at the L_2,3 of Co, the magnetic response of the film could be sensed at different distances from the interface. Data show a reduction of the magnetization at the interface though the existence of a magnetically 'dead' layer is completely ruled out. Moreover, the magnetization was found to be reduced at the Fe film surface

[en] Full text: The dependence of x-rays absorption spectra (XANES) of magnetized samples on the circular polarization of the photon is called x-rays Magnetic Circular Dichroism (XMCD). Whereas the similarities between XANES and energy loss near edge structures (ELNES) in the Transmission Electron Microscope (TEM) succeeded to export linear dichroism to the TEM, a similar task for circular dichroism was considered impossible. A recent discovery shows that this is not true. 10 nm of Iron were deposited on a GaAs (001) disk previously thinned to electron transparency. Measurements of transverse and longitudinal magneto-optic KEXrr effect showed evidence of residual in-plane magnetization. XMCD measurements have been performed by aligning the residual magnetization of the sample and the photon spin parallel and antiparallel. The dichroic signal is obtained by scanning in energy over the Fe L_2,3 edges and either by reversing the circular polarization handness from the undulator radiation source, or by rotating the sample of π rad. XMCD signals with typically 33 % asymmetry at the L₃ edge were obtained. To measure the Energy-loss Magnetic Chiral Dichroism (EMCD) in the TEM, an interferometric technique is used: the polarization vector ^→e of light corresponds to the momentum transfer ^→q of the electron to the target. The crystal itself serves as beam splitter and dephaser, to obtain an excitation corresponding to left-/right-handed circularly polarized light. This can be achieved by choosing two particular EELS detector positions in the diffraction plane. EMCD and XMCD have been detected on the same Fe sample, thus establishing the first direct comparison. (author)

[en] A 3-layer edge-on silicon microstrip detector for the SYRMEP/FRONTRAD project has been designed and realised. The image matrix is made by 764 pixels with dimensions 300 (thickness of the single detectors) x 200 (strip pitch) μm². The system has a sensitive area of 50 x 1 mm², an inter-layer distance of ∼ 100 μm and an efficiency of ∼ 80% for 20 keV photons. The image is acquired by scanning the object across the beam cross-section and the overall statistics on the single pixel is obtained by summing up the information of corresponding pixels in the three layers, thereby reducing the effect of possible noisy or not functioning pixels. Experimental results obtained at the SYRMEP/FRONTRAD beam line of the ELETTRA synchrotron radiation machine with this innovative detector are presented