Karine CHESNEL ALS WORKSHOP Magnetic Nanostructures, Interfaces, and New Materials: Theory,...
-
Upload
rosaline-perry -
Category
Documents
-
view
216 -
download
0
Transcript of Karine CHESNEL ALS WORKSHOP Magnetic Nanostructures, Interfaces, and New Materials: Theory,...
Karine CHESNELALS
WORKSHOPMagnetic Nanostructures,
Interfaces, and New Materials: Theory, Experiment, and Applications
Collaborations
“Flangosaurus”
Zahid Hussain, ALS Support Tom Miller, Soren Prestemon, John Spring, John Pepper, …
Steve Kevan University of OregonJoshua Turner
Jeffrey Kortright Lawrence Berkeley Lab
Eric Fullerton Hitachi, San Jose
Olav Hellwig (BESSY, Germany)
Larry Sorensen University of WashingtonMichael Pierce
Shouheng SUN IBM, New York
Kannan KRISHNAN University of Washington
K.Chesnel
OutlineOutline
IntroductionIntroduction
The coherent scattering endstation at ALSThe coherent scattering endstation at ALS
First investigations on nanoparticlesFirst investigations on nanoparticles
Different way to use magnetic Speckle Different way to use magnetic Speckle
K.Chesnel
How obtaining magnetic speckles?
Magnetic Structure
(nanoscale)
Coherentillumination
Pinhole
Spatial filtering:
Transversecoherence
Light(Soft X)
TemporalCoherence
Detector
ResonantScattering
Magnetic Speckle pattern
Short range magnetic orderLocal disorder
J. Kortright K.Chesnel
Coherent Soft X-Ray Beamline (BL12.0.2)
Optimization of the beam
= 2.48 nm (500 eV)d = 2.5 µm
Rosfjord et al. (2004)
Energy range 200-1000eV
Coherent flux at 500eV:~ 5 1010 ph/sec/0.1%BW
K.Chesnel
Scatteringin
Transmission
X rays
Samplelocation
Coherent Soft X-ray Magnetic Scattering endstation
Flangosaurus
K.Chesnel
Scatteringin
Transmission
ScatteringIn Reflection
X rays
Samplelocation
Flangosaurus
K.Chesnel
Flangosaurus
Octopolar magnetUnit pole
H
x
y
z
Produce Magnetic field in any directionMaximal amplitude 0.6 T
WaterCoolingsystem
CurrentInput
(100A)
K.Chesnel
Flangosaurus
Scatteringchamber
Light
Opticaltable
CryogenicSample-holder
Magnetic manipulator
Load-lockchamber
Bellow
Samplelocation
Rotationbrackets
Pressure10-8 mBar
K.Chesnel
Flangosaurus:Cryogenic Sample holder + pinhole mechanism
feedback
InchwormBender
Sampleholder
3 pinholesholder
HorinzontalMotion
(13 mm)
VerticalMotion
(1.5 mm)
5 mm
Pinhole size: few mGood oversampling
Near field
Mechanicalisolation
K.Chesnel
• Control of pinhole positioning
• High oversampling condition
• In-situ 3D magnetic field
• Sample cooling (cryostat)
• Investigation of the full main scattering
plane
• 2D detection with high resolution
• Fast detection
Experimental possibilitiesExperimental possibilities
K.Chesnel
Different geometries specificitiesDifferent geometries specificities
• Any kind of substrate
• Possibility to vary the incidence angle (f’,f’’)
• Depth sensitivity
• Discrimination of themagnetic components
ReflectionReflection• Use of membrane
• Simple measure of transmitted light (f’’)
• Direct image in the reciprocal space
• Transmitted beam easy to block
TransmissionTransmission
K.Chesnel
Probing the magnetism in nanoparticlesProbing the magnetism in nanoparticles
-6 10-7
-4 10-7
-2 10-7
0
2 10-7
4 10-7
6 10-7
8 10-7
0 50 100 150 200 250 300 350
P11A10 ZFC/FC
Temperature
Super-paramagnetic
Blocked
Blocking temperature
Resonant soft X-ray scattering
- Probe the magnetic order/disorder- effect of field and temperature- slow and fast dynamic
Co nanoparticles Self-assembly
Mesoscopic Scale
~10nm particles
Magnetic configuration
of the nanoparticles ?
?
K.Chesnel
Probing the magnetism in nanoparticlesProbing the magnetism in nanoparticles
Different systems under study:
Co particles 8-9nm (variable packing)Co particles 8-9nm (variable packing)
FeFe33OO44 particles variable size 4-16nm particles variable size 4-16nm
Sources S. Sun, K Krishnan…
Kortright et al. (2004)
I0
Magnetic fieldScattered light
(SAXS)
Transmitted light (XMCD)
Transmission geometryIncoherent light XMCD, SAXS
(average information)
Coherent light speckle pattern (average information)
K.Chesnel
Characterization with polarized light (BL4)Characterization with polarized light (BL4)
750 760 770 780 790 800
-0.04
-0.03
-0.02
-0.01
0.00
0.01
0.02
0.03750 760 770 780 790 800
200
400
600
800
1000
1200
1400
1600
XMCD
Energy (eV)
Co nanocrystals: Sample 2
Transmitted intensity plus minus L3 L2
XMCD
0.1 0.2 0.3 0.4 0.5 0.6
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
F
Normalized intensity
q (nm-1)
Co Nanoparticles
AF
Incoherent scattering
Co L3 edgeInterparticle
distance~12nm
Correlation length~60nm
-10 -5 0 5 100.095
0.100
0.105
0.110
0.115
0.120
0.125
0.130
0.135
Intensity
Field (kG)
P+ P-
AF peak
beam current normalization
25% XMCD
-10 -5 0 5 1024
26
28
30
32
34
36
38
Intensity
Field (kG)
P+ P-
FERRO peak
beam current normalization
35% XMCD
I0
Magnetic fieldScattered light
(SAXS)
Transmitted light (XMCD)
Co nanocrystals
K.Chesnel
Coherent 2D scattering on nanoparticles
Co Nanoparticles assemblyprecipitated on TEM grid
X –ray beamtuned to resonant edge
Diffuse scattering
Pinhole(coherence)
CCDCamera2048x2048
Energy optimized at Co L3 edge: =1.58 nm
750 760 770 780 790 800 810 820 8300
2
4
6
8
10
12
14
16
18
20
Intensity (normalized)
energy (eV)
integration of diffuse peak normalized by M5
L3
L2
Co nanoparticles (A9)
K.Chesnel
TEM image (K.Krishnan)
VERY HERTEROGENEOUS!!
Localized peaks => Ordered
area
IsotropicPattern
Another Ordered area
General 2D scattering Patterns (no pinhole)
ALL patterns distributed along a RING
• ordered area d~ 12nm• disordered d~ 13nm
K.Chesnel
Effect of magnetic field in linear polarization
X rays
Hperp
Hpar
Scattering peak (charge +magnetic)
Fullscattering
DifferenceRemanence-Saturation
With PERPENDICULAR field: I (saturation) > I (remanence)
(Effect ~0.5%)
With IN PLANE field: I (saturation) < I (remanence)
At saturation all particle moment are pointing the same direction and contribute to the peak
With linear polarisationX rays are not sensitive to the in plane component
- Ordered area
K.Chesnel
Effect of magnetic field – isotropic area
X rays
Hperp
Hpar
With PERPENDICULAR field: I (saturation) > I (remanence)
Effect ~4%
DifferenceRemanence - Saturation
Full scattering
Scattering signal(charge +magnetic)
It seems isotropic areas show a strongertendency to AF order at remanence, while ordered area are more F…
K.Chesnel
Obtaining a Speckle pattern:Obtaining a Speckle pattern: degree of coherence/ pinhole size (Co edge) degree of coherence/ pinhole size (Co edge)
200 400 600 800 1000 1200 1400 1600 1800 2000
200
400
600
800
1000
1200
1400
1600
1800
2000
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
x 104
200 400 600 800 1000 1200 1400 1600 1800 2000
200
400
600
800
1000
1200
1400
1600
1800
20000
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
No pinhole 10sec
5 m pinhole 100s 3 m pinhole 300s
C=1%
200 400 600 800 1000 1200 1400 1600 1800 2000
200
400
600
800
1000
1200
1400
1600
1800
2000
0.5
1
1.5
2
2.5
3
3.5
4
4.5
x 104
25 m pinhole 100s
C=3%
C=12%
200 400 600 800 1000 1200 1400 1600 1800 2000
200
400
600
800
1000
1200
1400
1600
1800
20000
200
400
600
800
1000
1200
1400
1600
1800
2000
C=25%
NC
1∝
…Dainty law
Transverse coherence
lengthc~1m
K.Chesnel
Static spatial cross correlation (metrology)Static spatial cross correlation (metrology)Slow dynamic on spatial correlationSlow dynamic on spatial correlationFast dynamic time correlationFast dynamic time correlation
What the Speckle pattern tell us?What the Speckle pattern tell us?
Speckle pattern Autocorrelation pattern
Specklesize
Background(incoherentScattering)
Three Ways to use the speckle
K.Chesnel
1. Static Speckle metrology1. Static Speckle metrology
Cross-correlationbetween two
speckles patternsA and B
A
B
( ) [ ][ ] [ ]∑ ∑∑
⊗⊗
⊗>=<
BBAA
BABA,ρ
Correlation coefficient
Magnetic Memory
Pierce et al. PRL 90, 175502 (2003)
= 0 no memory= 1 total memory(exact same pattern)
K.Chesnel
Major Loop Return and Conjugate Point Memory
major loopA
B
C
A Starting pointB Conjugate PointC Return Point
A x B = CPMA x C = RPM
1 2 3 4 50.75
0.80
0.85
0.90
0.95
1.00
RPM
CPM
RPM
Rho
image number
perpendicular field in-plane field
perpendicular field in-plane field
CPM
Cross correlation
Ordered area
Disordered area
VERY HIGH MEMORY ! K.Chesnel
2. Slow dynamic2. Slow dynamic
Diffuse ring(disordered area)
Each frame: 10 sec
Diffuse ring(disordered area)Each frame: 3 sec
Evolution of the slow dynamic versus temperature
• Speckle correlationdecreases with time• Decay slope depends on temperature
K.Chesnel
Price, Sorensen, Kevan et al. PRL 82, 755 (1999)
Time autocorrelation
∫ −= dttItIg )().()( ττ
MCP
HV
PositionAnalyzer
DigitalCorrelator
Pre-amp
X
Y
Z
Oscilloscope in XY mode
Detector
Scattering signal
Time scale:sec1sec1 <<τ
ScatteringSignal
I (t)
Principle
3. Fast dynamic3. Fast dynamic
K.Chesnel
Fast dynamic measurements: First results on Fe3O4 nanoparticles
1E-3 0.01 0.1 1 10 100 10000
1
2
3
4
5
6
7
8
9
10
Accessible range forsample fluctuations
Synchrotron
noise
Time Autocorrelations on Nanoparticles
Autocorrelation
Lag time (ms)
Afterpulsingeffect
0.1 1 10
1.00
1.01
1.02
1.03
1.04 Measurment Exp decay fit
Autocorrelation
Lag time (ms)
τ=1.7ms
Fe L3 edge25 m pinhole/sample300 m hole/detector
Intensity 15 000 cps/sec
• Evolution with T (through blocking transition)• Effect of magnetic field
Map the dynamic (H,T)K.Chesnel
ConclusionConclusion
New endstation for coherent magnetic scattering New endstation for coherent magnetic scattering now functional at ALS BL12now functional at ALS BL12
First investigations on Co and Fe3O4 nanoparticles First investigations on Co and Fe3O4 nanoparticles with coupled measurements in with coupled measurements in incoherentincoherent light (XMCD, light (XMCD, SAXS) and SAXS) and coherentcoherent light (speckle) light (speckle)
Static speckle study: magnetic memoryStatic speckle study: magnetic memory
Slow dynamic: time scale > 1sec Slow dynamic: time scale > 1sec
Fast dynamic: time scale 10 Fast dynamic: time scale 10 sec – 1secsec – 1sec
K.Chesnel
“Speckle” techniques
• Speckle Metrology (spatial)
• Slow and fast dynamic
• Lensless magnetic imaging
Candidates
•Metallic thin filmsCo/Pt, FePd, FePt…
• Patterned media
• Nanoparticles
• Exchange bias
• Manganites CMR
• Cuprates superconductivity
Physics
• Local magnetic configuration
• Magnetic memory
• Spatiotemporal fluctuations
• (Temperature, field) transitionsK.Chesnel