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The redox reaction between natural Fe-containing clay minerals and its sorbates is a fundamental process controlling the cycles of carbon, nutrients, and inorganic as well as organic pollutants in Earth’s critical zone. While the structure of natural clay minerals under oxic conditions is well known, this is not true for anoxic conditions, thereby impeding a full understanding of the mechanisms of clay-driven redox reactions especially under reducing conditions. Here we investigate the structure of an Fe-rich natural clay mineral, nontronite, under different redox conditions, and compare several methods for the determination of iron redox states. Nontronite was gradually reduced chemically with the Citrate-Bicarbonate-Dithionite (CBD) method. All methods used to determine the Fe redox state, i.e. 57Fe Mössbauer spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) spectroscopy including its pre-edge, extended X-ray absorption fine structure (EXAFS) spectroscopy, and mediated electrochemical oxidation and reduction (MEO/MER), provided consistent Fe(II)/Fe(III) ratios. By combining X-ray diffraction (XRD) and Transmission electron microscopy (TEM), we show that the long-range structure of nontronite at the highest obtained reduction degree of 44% is not different from that of fully oxidized nontronite except for a slight basal plane dissolution on the external surfaces. The short-range order probed by EXAFS spectroscopy suggests, however, an increasing structural disorder and Fe clustering with increasing reduction of structural Fe.

Titanium and its alloys possess a range of highly interesting properties such as excellent corrosion resistance, high specific strength and biocompatibility, but suffers from poor wear resistance. The present work addresses plasma assisted surface treatment of CP 2 titanium using various combinations of oxygen and nitrogen, i.e. mixed interstitials. The sequence of controlled plasma nitriding and oxidizing treatments plays a significant role for the evolution of the hardness depth profiles and the development of the surface compound layer and the underlying diffusion/transition zone. Composition profiles of oxygen and nitrogen are obtained by GDOES; Mixed interstitial solubility of nitrogen and oxygen is found in both h.c.p. α titanium and in the compound layer. The combination of interstitials leads to larger case depth, in particular for the diffusion zone (expanded h.c.p. α titanium). Therefore, it highlights the advantages of combined nitriding and oxidizing compared to single nitriding treatments on the mechanical properties.

30 keV Ga+ irradiation-induced changes of magnetic and magneto-optical properties of sputtered Pt/Co/Pt ultrathin trilayers films have been studied as a function of the ion fluence. Out-of-plane magnetic anisotropy states with enhanced magneto-optical e ects were evidenced for specific values of cobalt thickness and irradiation fluence. Results obtained after uniform or quasi-uniform focused ion beam irradiation on either out-of-plane or in-plane magnetized sputtered pristine trilayers are compared. Similar irradiation-induced magnetic changes are evidenced in quasi-uniformly focused ion beam or uniformly irradiated films, grown either by sputtering or molecular beam epitaxy. We discuss on plausible common mechanisms underlying the observed effects.

Coherent x-ray diffractive imaging is a powerful method for studies on nonperiodic structures on the nanoscale. Access to femtosecond dynamics in major physical, chemical, and biological processes requires single-shot diffraction data. Up to now, this has been limited to intense coherent pulses from a free electron laser. Here we show that laser-driven ultrashort x-ray sources offer a comparatively inexpensive alternative. We present measurements of single-shot diffraction patterns from isolated nano-objects with a single 20 fs pulse from a table-top high-harmonic x-ray laser. Images were reconstructed with a resolution of 119 nm from the single shot and 62 nm from multiple shots.

In Pt/Co(d)/Pt ultrathin film structures a spin reorientation transition (SRT) from out-of-plane to in-plane magnetization states is known to occur at a critical Co thickness d=dSRT ~ 1.8nm. For thinner Co thicknesses this SRT can also be forced by ion irradiation. In the present work we demonstrate that also the reverse SRT, i. e. from in-plane to out-of-plane, can be achieved by ion irradiation in certain cases. Therefore, easy-plane magnetized Pt/Co(3nm)/Pt samples were irradiated by 30 keV Ga+ ions with doses D ranging from 1014 to 5x1016 ions/cm2. The ion irradiation induced effects were investigated by polar magnetooptical microscopy, magnetometry and atomic/magnetic force microscopy. At low dose the reverse SRT is observed with a large out-of-plane magnetization component giving rise to a square perpendicular hysteresis loop. Sub-micrometer perpendicular magnetic domain structures either field-induced or in the demagnetized state confirm this new behavior. At higher dose, the easy magnetization direction is turned in-plane again. Topologically, a film swelling effect is first evidenced at low dose, but surface etching dominates at higher dose. Similar effects are also observed under quasi-uniform irradiation performed by scanning a focused ion beam (FIB) on the Pt/Co(3nm)/Pt structure. The results will be also compared to those reported earlier for d < dSRT, where ion irradiation leads to a reduction of the Curie temperature, coercivity and magnetic anisotropy [1,2]. This work was partially supported by EU MC TOK project NanomagLab No MTKD-CT-2004-003177 and EU-RITA program “Centre for Application of Ion Beams in Materials Research” under contract no. 025646. J.J. has benefited of an EC Marie-Curie fellowship (contract MEST CT 2004-51437). [1] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, H. Kronmüller, S. Parkin (eds), (2007) John Wiley & Sons, Ltd. [2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320 (2008) 579.

In Pt/Co(d)/Pt ultrathin film structures a spin reorientation transition (SRT) from out-of-plane to in-plane magnetization states is known to occur at a critical Co thickness d=dSRT ~ 1.8nm. For thinner Co thicknesses this SRT can also be forced by ion irradiation. In the present work we demonstrate that also the reverse SRT, i. e. from in-plane to out-of-plane, can be achieved by ion irradiation in certain cases. Therefore, easy-plane magnetized Pt/Co(3nm)/Pt samples were irradiated by 30 keV Ga+ ions with doses D ranging from 1014 to 5x1016 ions/cm2. The ion irradiation induced effects were investigated by polar magnetooptical microscopy, magnetometry and atomic/magnetic force microscopy. At low dose the reverse SRT is observed with a large out-of-plane magnetization component giving rise to a square perpendicular hysteresis loop. Sub-micrometer perpendicular magnetic domain structures either field-induced or in the demagnetized state confirm this new behavior. At higher dose, the easy magnetization direction is turned in-plane again. Topologically, a film swelling effect is first evidenced at low dose, but surface etching dominates at higher dose. Similar effects are also observed under quasi-uniform irradiation performed by scanning a focused ion beam (FIB) on the Pt/Co(3nm)/Pt structure. The results will be also compared to those reported earlier for d < dSRT, where ion irradiation leads to a reduction of the Curie temperature, coercivity and magnetic anisotropy [1,2]. This work was partially supported by EU MC TOK project NanomagLab No MTKD-CT-2004-003177 and EU-RITA program “Centre for Application of Ion Beams in Materials Research” under contract no. 025646. J.J. has benefited of an EC Marie-Curie fellowship (contract MEST CT 2004-51437). [1] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, H. Kronmüller, S. Parkin (eds), (2007) John Wiley & Sons, Ltd. [2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320 (2008) 579.

In Pt/Co(d)/Pt ultrathin film structures a spin reorientation transition (SRT) from out-of-plane to in-plane magnetization states is known to occur at a critical Co thickness d=dSRT ~ 1.8nm. For thinner Co thicknesses this SRT can also be forced by ion irradiation. In the present work we demonstrate that also the reverse SRT, i. e. from in-plane to out-of-plane, can be achieved by ion irradiation in certain cases. Therefore, easy-plane magnetized Pt/Co(3nm)/Pt samples were irradiated by 30 keV Ga+ ions with doses D ranging from 1014 to 5x1016 ions/cm2. The ion irradiation induced effects were investigated by polar magnetooptical microscopy, magnetometry and atomic/magnetic force microscopy. At low dose the reverse SRT is observed with a large out-of-plane magnetization component giving rise to a square perpendicular hysteresis loop. Sub-micrometer perpendicular magnetic domain structures either field-induced or in the demagnetized state confirm this new behavior. At higher dose, the easy magnetization direction is turned in-plane again. Topologically, a film swelling effect is first evidenced at low dose, but surface etching dominates at higher dose. Similar effects are also observed under quasi-uniform irradiation performed by scanning a focused ion beam (FIB) on the Pt/Co(3nm)/Pt structure. The results will be also compared to those reported earlier for d < dSRT, where ion irradiation leads to a reduction of the Curie temperature, coercivity and magnetic anisotropy [1,2]. This work was partially supported by EU MC TOK project NanomagLab No MTKD-CT-2004-003177 and EU-RITA program “Centre for Application of Ion Beams in Materials Research” under contract no. 025646. J.J. has benefited of an EC Marie-Curie fellowship (contract MEST CT 2004-51437). [1] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, H. Kronmüller, S. Parkin (eds), (2007) John Wiley & Sons, Ltd. [2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320 (2008) 579.

In Pt/Co(d)/Pt ultrathin film structures a spin reorientation transition (SRT) from out-of-plane to in-plane magnetization states is known to occur at a critical Co thickness d=dSRT ~ 1.8nm. For thinner Co thicknesses this SRT can also be forced by ion irradiation. In the present work we demonstrate that also the reverse SRT, i. e. from in-plane to out-of-plane, can be achieved by ion irradiation in certain cases. Therefore, easy-plane magnetized Pt/Co(3nm)/Pt samples were irradiated by 30 keV Ga+ ions with doses D ranging from 1014 to 5x1016 ions/cm2. The ion irradiation induced effects were investigated by polar magnetooptical microscopy, magnetometry and atomic/magnetic force microscopy. At low dose the reverse SRT is observed with a large out-of-plane magnetization component giving rise to a square perpendicular hysteresis loop. Sub-micrometer perpendicular magnetic domain structures either field-induced or in the demagnetized state confirm this new behavior. At higher dose, the easy magnetization direction is turned in-plane again. Topologically, a film swelling effect is first evidenced at low dose, but surface etching dominates at higher dose. Similar effects are also observed under quasi-uniform irradiation performed by scanning a focused ion beam (FIB) on the Pt/Co(3nm)/Pt structure. The results will be also compared to those reported earlier for d < dSRT, where ion irradiation leads to a reduction of the Curie temperature, coercivity and magnetic anisotropy [1,2]. This work was partially supported by EU MC TOK project NanomagLab No MTKD-CT-2004-003177 and EU-RITA program “Centre for Application of Ion Beams in Materials Research” under contract no. 025646. J.J. has benefited of an EC Marie-Curie fellowship (contract MEST CT 2004-51437). [1] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, H. Kronmüller, S. Parkin (eds), (2007) John Wiley & Sons, Ltd. [2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320 (2008) 579.