Study of ultrathin Pt/Co/Pt trilayers modified by nanosecond XUV pulses from laser-driven plasma source

We have studied the structural mechanisms responsible for the magnetic reorientation between in-plane and out-of-plane magnetization in the (25 nm Pt)/(3 and 10 nm Co)/(3 nm Pt) trilayer systems irradiated with nanosecond XUV pulses generated with laser-driven gas-puff target plasma source of a narrow continuous spectrum peaked at wavelength of 11 nm. The thickness of individual layers, their density, chemical composition and irradiation-induced lateral strain were deduced from symmetric and asymmetric X-ray diffraction (XRD) patterns, grazing-incidence X-ray reflectometry (GIXR), grazing incidence X-ray fluorescence (GIXRF), extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) measurements. In the as grown samples we found, that the Pt buffer layers are relaxed and that the layer interfaces are sharp. As a result of a quasi-uniform irradiation of the samples, the XRD, EXAFS, GIXR and GIXRF data reveal the formation of two distinct layers composed of Pt1-xCox alloys with different Co concentrations, dependent on the thickness of the as grown magnetic Co film but with similar ∼1% lateral tensile residual strain. For smaller exposure dose (lower number of accumulated pulses) only partial interdiffusion at the interfaces takes place with the formation of a tri-layer composed of Co-Pt alloy sandwiched between thinned Pt layers, as revealed by TEM. The structural modifications are accompanied by magnetization changes, evidenced by means of magneto-optical microscopy. The difference in magnetic properties of the irradiated samples can be related to their modification in Pt1-xCox alloy composition, as the other parameters (lateral strain and alloy thickness) remain almost unchanged. The out-of-plane magnetization observed for the sample with initially 3 nm Co layer can be due to a significant reduction of demagnetization factor resulting from a lower Co concentration

Structure perfection variations of Si crystals grown by Czochralski or floating zone methods after implantation of oxygen or neon atoms followed by annealing

Structure perfection of the silicon crystals grown by the Czochralski and floating zone methods after implantation with oxygen or neon fast iones followed by annealing at the temperatures T ~ 1050-1150 ⁰0C, when large SiOx precipitates were formed, was studied by means of various X-ray diffraction methods. Considerable increments of integral reflectivities for different Bragg reflections of such samples in comparison with those calculated for a perfect crystal were detected. Broadening of the spatial intensity distribution curves for the Bragg-diffracted beams taken by a single crystal spectrometer as well as the maps of the diffuse isointensity distribution near a reciprocal lattice point, registered by the Philips high-resolution diffractometer, are shown. All of these diffraction effects related to creation of the SiOx precipitates formed on structural damages caused by implantation of oxygen or neon ions and subsequent annealing. Contrary to FZSi, where the appearence of SiOx precipitates was discovered due to intensive diffuse scattering near the layer contained the implanted oxygen ions only, in the case of CZSi samples with larger concentration of oxygen (up to 1*10¹⁸ at/cm³) such defects were formed not only near the burried layer, created by ions of oxygen or neon (with energy E = 4 MeV, dose 10¹⁴cm⁻²) but in a bulk of a crystal. Annealing of the FZSi crystals implanted by oxygen (E ~ 200 keV, dose ~ 10¹⁶-10¹⁷ cm⁻²) at enhanced hydrostatic pressure, additionally stimulated SiOx precipitation close to the implanted layer

Investigations of surface morphology and microrelief of GaAs single crystals by complementary methods

The paper presents the study of morphology and roughness of (100) surfaces of GaAs single crystals grown by the Czochralski method. The surfaces were prepared in a different way: mechanical polishing, chemomechanical polishing, mechanical grinding, wet polishing etching, anisotropic etching. The X-ray grazing incidence reflectivity, atomic force microscopy, scanning tunneling microscopy, optical specular reflection, and profilometric methods were complementary used. The application of these methods allowed to reveal the details of differences in the surface morphology varied with the way of its preparation

XAFS Study of Fe Intercalated Fullerite

Fe K edge XANES and EXAFS studies were performed to reveal the local structure around Fe ions in C60Fe2 fullerites. The measurements were carried out in transmission mode at LN2 temperature for the monoclinic and fcc C60Fe2 fullerite powder samples and other materials : ferrocene Fe(C5H5)2. Fe metal foil and α-Fe2O3. The XAFS spectra of the monoclinic C60Fe2 fullerite is almost identical to that of ferrocen. The XAFS spectra of the fcc C60Fe2 fullerite have shown that Fe neutral atoms, Fe2+ and Fe3+ ions appear in this fullerite due to annealing at temperature 850 K. The EXAFS study has proved the presence of small Fe clusters in this form of fullerite