Transcript No Slide Title

Resonant soft X-ray sc attering strudies of the magnetic nanostructure of strip e domains
Uitnodiging
Resonant soft x-ray scattering
studies of
the magnetic nanostructure
of stripe domains
Op donderdag 19 jun i 2003
om 10. 00 uur
zal ik mijn p roefsc hrift
verdedigen.
U bent bij deze van harte
uitgenodigd om hierbij
aa nwezig te zijn. De
plechtigheid za l plaatsvinden in
de Aula der Universiteit
van Amsterdam ,
Ou de Lutherse Kerk,
Sin gel 411 (hoek S pui).
June 19 10:00
Na afloop is er een receptie
Resonant soft X-ray
scattering studies of
the magnetic nanostructure of stripe
domains
Joost Peters
[email protected] va.nl
J.F. Peters
Paranimfen:
J eroen Bongaerts
bong [email protected] va.nl
2
Jorge Miguel
Together with
Van der Waals Zeeman Institute
ID08/ID12B
Mark de Vries
Nick Brookes
Olivier Toulemonde
Sarnjeet Dhesi
Jorge Miguel
Kenneth Larsson
Huib Luigjes
Jeroen Goedkoop
Friso van der Veen
Michel Zwanenburg
Jeroen Bongaerts
Ekkes Brück
TROIKA
Carsten Detlefs
Gerhard Gruebel
Motivation
Magnetism of confined systems:
• Thin films, surfaces, wires, clusters
• What happens when dimensions approach fundamental length scales
• Fundamental discoveries foster technological progress and vice versa
Soft X-rays as a magneto-optical probe
• 1 nm wavelength
• Element specifity
• Submonolayer sensitivity
X-ray Resonant Magnetic Scattering (XRMS)
Kerr Microscopy
This talk…..
• Stripe domains, domain walls and closure domains
• X-ray magneto-optics: absorption and dispersion
• Magnetic diffraction: polarization and energy dependence
• Evolution of stripes over the in-plane magnetization loop
Stripe domains
Shape anisotropy
Uniaxial anisotropy
z
Strong stripes
y
x
Closure domains
Weak stripes
As grown
After 1 Tesla
5 m
Stripe domains in a
40 nm GdFe5 thin
film
This talk…..
• Stripe domains, domain walls and closure domains
• X-ray magneto-optics: absorption and dispersion
• Magnetic diffraction: polarization and energy dependence
• Evolution of stripes over the in-plane magnetization loop
X-ray Magnetic Resonant Scattering
I
iqrn
e
n Fn
M
2
Fn scattering amplitude
e
e’ k '

q
k
At absorption resonance:
polarisation-dependent magnetic contributions
Fn
~ number of
( 0)
ˆ
ˆ
 electrons/ato
e'eFn  i(eˆ ' x
m
How to find F0, F1, F2?
ˆ F (1)  (eˆ 'M
ˆ )(eˆ  M
ˆ ) F ( 2)
ˆe)  M
n n
n
n
n
Spectroscopy !
X-ray absorption spectra Gd M45 (3d 4f)
XAS
=Im(F(o))
XMCD=XAS(+)-XAS(-)
= Im(F(1))
+M
-M
ê
zz
ê’
XMLD=XAS(//)-XAS()
= Im(F(2))
M
ê
Myx
ê’
Resonance
Gd M4,5
From absorption cross section
to scattering cross section
atomic scattering amplitude:
f ( )  Z  f ' ( )  if '' ( )
imaginary part: absorption
 a ( )
f " ( ) 
2re 
real part: Kramers-Kronig
1
f ' (E) 
re hc

 2 a ( )
0 E 2   2 d
This talk…..
• Stripe domains, domain walls and closure domains
• X-ray magneto-optics: absorption and dispersion
• Magnetic diffraction: polarization and energy dependence
• Evolution of stripes over the in-plane magnetization loop
ESRF
European Synchrotron Radiation Facility
Experimental setup
+
+
A
A
transmission
grid
photodiode
sample
mirror
beam
vertical/
horizontal slits
Diffraction patterns of disordered and aligned stripes
0
1
-3
2
100 m beam
Gd M5 edge
-2 -1
0
1
2
3
Scattered/Transmitted intensity
Is/It=|F(1)|2
Aligned stripe domains
y
k
x
k
Energy dependence of diffraction orders
Odd orders follow F1()
Even orders follow F2 ()
Aligned stripe domains
B=0
ey
ex
F(1) Mz
Mz Mxy
F(2) My2
F(2) Mx2
This talk…..
• Stripe domains, domain walls and closure domains
• X-ray magneto-optics: absorption and dispersion
• Magnetic diffraction: polarization and energy dependence
• Evolution of stripes over the in-plane magnetization loop
Magnetic diffraction in applied fields
kerr loop
B
290 K
d
z
x
P
B
20 K
y
Period
Intensity
Peakwidth/position
Angular HWHM
Mx^2
Intensities vs. field
x-polarization (domain walls)
y-polarization (closure domains)
1
2
3
4
5
6
A
A
D
H
B
C
F
B
H
C
H
D
H
E
H
F
z
x
H
y
Resonant Magnetic Diffraction
Determination resonant
scattering amplitude
Polarization: 3D-magnetometry
Evolution of stripes over inplane magnetization curve
z
x
Absorption
Visible
UV
Visible, UV and
X-ray Absorption
4sp
band
Binding energy (eV)
3d band
60
3p
3s
600
2p
2s
6000
1s
X-ray Edges
M
L
2 3
L
1
K
A
H
B
H
C
H
D
H
E
H
F
z
x
H
y
d
z
x
P
y
air
vacuum
+
CCD
lens
A
photodiode
cold
finger
screen
beamstop
sample
+
+
A
A
transmission
grid
photodiode
sample
mirror
beam
vertical/
horizontal slits