SOFT X-RAY SCATTERING AT ESRF: A BRIEF OVERVIEW Peter Bencok European Synchrotron Radiation Facility Grenoble, France

OUTLINE ID8 Characteristics Scattering instruments: High field magnet setup Diffractometer setup Commissioning results Experimental results Development Conclusion

ID8 CHARACTERISTICS 2 undulators APPLE II 100 % polarized light of any polarization Dragon monochromator Energy range eV Resolving power Flux at the sample photons/s/0.1%BW Beam size 1 mm x 0.1 mm 5 experimental stations

HIGH FIELD MAGNET SETUP Generally devoted to XMCD 7 Tesla superconducting magnet Sample temperature K Horizontal scattering plane Diode detector with horizontal slit Prep. chamber : VT STM, LEED and AES + sample environment, preparation - reduced geometry

DIFFRACTOMETER SETUP 5-circle goniometer in 800 mm chamber Vertical scattering plane Entrance slits and pinholes Silicon pin diode with detector slits UVH compatible Timescale : Jan 2001Call for tender Oct 2002Delivery Oct 2003First user experiment

DIFFRACTOMETER SETUP Coaxially mounted external 2-circle stage coupled through differentially pumped rotary seals Other inside vacuum motors Base pressure < 1x mbar Preparation facility: chamber with ion sputtering, annealing, evaporation Sample stage connected to open-flow He cryostat that attains 80 K

COMMISSIONING RESULTS W/C Multilayers

COMMISSIONING RESULTS Off-specular scans FeGd films at the Fe L 3 edge absorption edge Various geometries allows different scattering channels Closure domains in FeGd alloy

EXPERIMENTAL RESULTS Orbital ordering in TM oxides S. S. Dhesi et al., PH YSICAL REVIEW LETTERS 92(5), (2004)

EXPERIMENTAL RESULTS Magnetic speckles from nanolines I magnetic speckles superlattice peaks specular peak x-ray beam pinhole 10 µm A. Marty, G. Beutier, G. van der Laan et al.

EXPERIMENTAL RESULTS Magnetic speckles from nanolines II Phase retrieval problem : I = |A|² I => A ? Small number of unknown, with discrete values => simulated annealing monte carlo algorithm after steps : Error ~ lines ~700 pixels between peaks  Oversampling >2 A. Marty, G. Beutier, G. van der Laan et al.

EXPERIMENTAL RESULTS 40 nm GdFe 180 nm period (MFM) Point symmetric, correlation ~ 0.93 Fraunhofer fringes Magnetic speckle from stripe domains in transmission J. B. Goedkoop, J. Peters, M. Vries, J. Miguel, O. Toulemonde, H. Luigjesp et al.

EXPERIMENTAL RESULTS EuSe nanoislands T. Schulli et al., APPLIED PHYSICS LETTERS 84(14), (2004)

EXPERIMENTAL RESULTS Co self-organisated nanodot network Au/1 ML Co/Au(11,12,12) Looking for the magnetic superstructure High surface sensitivity 60 nm S. Rousset, V. Repain, S. Rohart et al.

DEVELOPMENT Sample cooling: from 80K down to 21 K Magnetic field: 0.2 T pulsed perpendicular to the surface plane (in collaboration with Marty, van der Laan) 0.2 T static in the surface plane Polarization analysis: ML analyzer Area detector : CCD fixed on a flange Already done

CONCLUSION Successfully used for variety of experiments (OO, speckle, diffraction from nanostructures) Nowadays ~3 weeks of user experiments per 6 months but still requests for HFM setup Design of a diffractometer Versatility vs specialization in multiD space (H, T, angles, UHV, …) +- UHVin-situ preptransfer, materials,… Mom transfermore expspace, T, H ……… Modularity ? P.S. Different user requests for beam specification (speckle<>diffraction)

ACKNOWLEDGMENT S. S. DhesiDIAMOND N. Brookes S. Stanescu R. BarretESRF P. Marion P. van der Linden K. Larssonin memoriam A. Marty, G. BeutierCEA G. van der LaanSRS T. SchulliCEA G. Bauer, J.StanglUNIV Linz P. OhresserSOLEIL S. Rousset, V. Repain, S. RohartUNIV Paris 6 F. ScheurerIPCMS Strasbourg J. B. Goedkoop, J. Peters, M. VriesAmsterdam J. Miguel, O. Toulemonde, H. LuigjespAmsterdam