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SOFT X-RAY SCATTERINGAT ESRF: A BRIEF OVERVIEW
Peter BencokEuropean Synchrotron Radiation Facility
Grenoble, France
OUTLINE
ID8 CharacteristicsScattering instruments:
•High field magnet setup•Diffractometer setup
Commissioning resultsExperimental resultsDevelopmentConclusion
ID8 CHARACTERISTICS
2 undulators APPLE II100 % polarized light of any polarization
Dragon monochromatorEnergy range 400-1500 eVResolving power 5000-10000
Flux at the sample 1013 photons/s/0.1%BWBeam size 1 mm x 0.1 mm5 experimental stations
HIGH FIELD MAGNET SETUP
Generally devoted to XMCD7 Tesla superconducting magnetSample temperature 7-300 KHorizontal scattering planeDiode detector with horizontal slitPrep. chamber :
•VT STM, LEED and AES+ sample environment, preparation- reduced geometry
DIFFRACTOMETER SETUP
5-circle goniometer in 800 mm chamberVertical scattering planeEntrance slits and pinholesSilicon pin diode with detector slitsUVH compatible
Timescale :Jan 2001 Call for tenderOct 2002 DeliveryOct 2003 First user experiment
DIFFRACTOMETER SETUP
Coaxially mounted external 2-circle stage coupled through differentially pumped rotary sealsOther inside vacuum motorsBase pressure < 1x10-10 mbarPreparation facility: chamber with ion sputtering, annealing, evaporationSample stage connected to open-flow He cryostat that attains 80 K
COMMISSIONING RESULTS
W/C Multilayers
COMMISSIONING RESULTS
Off-specular scansFeGd films at the Fe L3
edge absorption edgeVarious 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), 56403-1-4 (2004)
EXPERIMENTAL RESULTS
Magnetic speckles from nanolines Imagnetic 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 350 000 steps :Error ~ 0.4
320 lines~700 pixels between peaks Oversampling >2
A. Marty, G. Beutier, G. van der Laan et al.
EXPERIMENTAL RESULTS
40 nm GdFe180 nm period
(MFM)
-1 0 1
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), 2661-3 (2004)
EXPERIMENTAL RESULTS
Co self-organisated nanodot network
Au/1 ML Co/Au(11,12,12)Looking for the magnetic superstructureHigh surface sensitivity
60 nm
0.2 0.4 0.6 0.8 1.0 1.2 1.4
1
2
3
4
5
6
hν = 778 (eVL3 )edge hν = 780 eV
( . )Intensity arb units
h
S. Rousset, V. Repain, S. Rohart et al.
DEVELOPMENT
Sample cooling: from 80K down to 21 KMagnetic 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 analyzerArea 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 requestsfor HFM setup
Design of a diffractometerVersatility 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 DIAMONDN. BrookesS. StanescuR. Barret ESRFP. MarionP. van der LindenK. Larsson in memoriamA. Marty, G. Beutier CEAG. van der Laan SRST. Schulli CEAG. Bauer, J.Stangl UNIV LinzP. Ohresser SOLEILS. Rousset, V. Repain, S. Rohart UNIV Paris 6F. Scheurer IPCMS StrasbourgJ. B. Goedkoop, J. Peters, M. Vries AmsterdamJ. Miguel, O. Toulemonde, H. Luigjesp Amsterdam