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					 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 400-1500 eV
     Resolving power 5000-10000
Flux at the sample 1013 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 7-300 K
Horizontal scattering plane
Diode detector with horizontal slit
Prep. chamber :
     •VT STM, LEED and AES
+ sample environment, preparation
- reduced geometry
  DIFFRACTOMETER SETUP


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

Coaxially mounted external 2-circle
stage coupled through differentially
pumped rotary seals
Other inside vacuum motors
Base pressure < 1x10-10 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

                                                             ds = 1 mm
                                                             ds = open
intensity (a.u.)




                   0.05   0.10    0.15         0.20   0.25       0.30
                                          -1
                                     qz (Å )
COMMISSIONING RESULTS


  Closure domains in FeGd alloy




                                  Off-specular scans
                                  FeGd films at the Fe L3
                                  edge absorption edge
                                  Various geometries
                                  allows different
                                  scattering channels
 EXPERIMENTAL RESULTS



                                              Orbital ordering in TM oxides




S. S. Dhesi et al., PH YSICAL REVIEW LETTERS 92(5), 56403-1-4 (2004)
   EXPERIMENTAL RESULTS

   Magnetic speckles from nanolines I
                                                  specular peak   magnetic
                                                                  speckles




superlattice peaks




                                             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



          320 lines                             after 350 000 steps :
          ~700 pixels between peaks             Error ~ 0.4
           Oversampling >2




 A. Marty, G. Beutier, G. van der Laan et al.
  EXPERIMENTAL RESULTS

Magnetic speckle from stripe domains in transmission
                            40 nm GdFe
                          180 nm period
                                 (MFM)




                  -1                0                1



                                           Fraunhofer
                                             fringes

                          Point symmetric, correlation ~ 0.93




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), 2661-3 (2004)
EXPERIMENTAL RESULTS

    Co self-organisated nanodot network

    Au/1 ML Co/Au(11,12,12)
    Looking for the magnetic superstructure
    High surface sensitivity

                                                                           6

                                                                                      h = 778 eV (L3 edge)
                                                                           5          h = 780 eV




                                                  Intensity (arb. units)
                                                                           4



                                                                           3

60 nm
                                                                           2



                                                                           1


                                                                               0.2   0.4      0.6      0.8       1.0   1.2   1.4

                                                                                                             h
        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, …)
                          +                         -
UHV                 in-situ prep         transfer, materials,…
Mom transfer         more exp                 space, T, H
                       ………
                    Modularity ?

P.S. Different user requests for beam specification (speckle<>diffraction)
ACKNOWLEDGMENT


S. S. Dhesi                             DIAMOND
N. Brookes
S. Stanescu
R. Barret                               ESRF
P. Marion
P. van der Linden
K. Larsson                              in memoriam
A. Marty, G. Beutier                    CEA
G. van der Laan                         SRS
T. Schulli                              CEA
G. Bauer, J.Stangl                      UNIV Linz
P. Ohresser                             SOLEIL
S. Rousset, V. Repain, S. Rohart        UNIV Paris 6
F. Scheurer                             IPCMS Strasbourg
J. B. Goedkoop, J. Peters, M. Vries     Amsterdam
J. Miguel, O. Toulemonde, H. Luigjesp   Amsterdam

				
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posted:10/7/2012
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