Obtaining soft x-ray constants Obtaining soft x-ray constants across the 2p edge of Fe in thin across the 2p edge of Fe in thin
films by resonant magnetic films by resonant magnetic scattering experiments of scattering experiments of
polarized soft X-rayspolarized soft X-rays
Fabian Walter, H.-Ch. Mertins, Fabian Walter, H.-Ch. Mertins,
Andreas Gaupp, Franz Schäfers, Andreas Gaupp, Franz Schäfers,
Wolfgang Gudat Wolfgang Gudat
Synchrotron RadiationSynchrotron Radiation
BESSY II BESSY II Synchrotron radiation as a light source. Synchrotron radiation as a light source. Radiation is produced by electrons radiating to due centripetal Radiation is produced by electrons radiating to due centripetal acceleration when following a circular path of about 240m acceleration when following a circular path of about 240m circumference near the speed of light (Peatman)circumference near the speed of light (Peatman)Advantages:Advantages:
Strong bundled light beamStrong bundled light beam Polarization and intensity can be precisely calculatedPolarization and intensity can be precisely calculated Coherence and time structureCoherence and time structure High intensity of the light beamHigh intensity of the light beam Continuous spectrum (Peatman)Continuous spectrum (Peatman)
UndulatorsUndulators Tuneable and known polarisation and intensityTuneable and known polarisation and intensity Polarisation of emitted light can thus be controlled to have circular and Polarisation of emitted light can thus be controlled to have circular and
linear components (Weiss, Sahwney)linear components (Weiss, Sahwney)
Undulator RadiationUndulator Radiation
Gap and shiftGap and shift
ApplicationApplication
Using synchrotron radiation for reflection and Using synchrotron radiation for reflection and transmission measurementstransmission measurements
Magnetooptical effectsMagnetooptical effects
Example: Determining optical constants for Example: Determining optical constants for magnetic materials such as Fe magnetic materials such as Fe Optical constants are not certainly known for many Optical constants are not certainly known for many
materials in the VUVmaterials in the VUV Needed for manufacturing of computational devicesNeeded for manufacturing of computational devices Knowledge of polarization of the incoming light beam Knowledge of polarization of the incoming light beam
enlarges possibilitiesenlarges possibilities
Magnetooptical Kerr-Effect (MOKE)
L-MOKE
2
B
T-MOKE
2
B
B
P-MOKE
2
Magnetic DichroismMagnetic Dichroism
)(1 in
TLTL
TLTLTL
RR
RRA
,,
,,,
BESSY Soft X-Ray Polarimeter BESSY Soft X-Ray Polarimeter
Polarizer Analyzer
CollimatorFilter
Multilayer
Frame Holder
Frame
P
A
2A
Io S =
(S0,S1,S2,S3)
h
Magazine
.
DetectorD
Fit curves for L-MokeFit curves for L-Moke
0 60 120 180 240 300 360
30
35
40
45
50
55
FWaltersample_fit
B-
B+
E=708.75eV
L-MOKE
100nm Fe
Inte
nsi
ty (
arb
. un
its)
azimuthal angle (deg)
data fit
Magnetic DichroismMagnetic Dichroism
)(1 in
TLTL
TLTLTL
RR
RRA
,,
,,,
Fit curves for L-MokeFit curves for L-Moke
0 60 120 180 240 300 360
30
35
40
45
50
55
FWaltersample_fit
B-
B+
E=708.75eV
L-MOKE
100nm Fe
Inte
nsi
ty (
arb
. un
its)
azimuthal angle (deg)
data fit
Asymetry in L-MOKEAsymetry in L-MOKE
0 60 120 180 240 300 360
0,20
0,25
0,30
0,35
0,40
L-MOKE
100nm Fe
FWalterlasymetries
asym
etry
azimuthal angle (deg)
E=707.5 eV E=708.75 eV E=709.25 eV
Fit curves in T-MOKEFit curves in T-MOKE
0 60 120 180 240 300 36032
34
36
38
40
42
44
46
48
50
52
FWaltersample_fit
B-
B+
E=708.75eV
T-MOKE
100nm Fe
Inte
nsi
ty (
arb
. un
its)
azimuthal angle (deg)
data fit
Asymetry in T-MOKEAsymetry in T-MOKE
0 60 120 180 240 300 3600,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
T-MOKE
100nm Fe
FWaltertasymetries
asym
etry
azimuthal angle (deg)
E=707.5 eV E=708.75 eV E=709.25 eV
Results for non-magnetic termsResults for non-magnetic terms
704 706 708 710 712 714 716 718
-0,002
-0,001
0,000
0,001
0,002
0,003
0,004
0,000
0,001
0,002
0,003
0,004
0,005
0,006
0,007
100nm Fe
FWalteroptical_constants
energy (eV)
Results for magnetic termsResults for magnetic terms
704 706 708 710 712 714 716 718-0,0015
-0,0010
-0,0005
0,0000
0,0005
0,0000
0,0002
0,0004
0,0006
0,0008
0,0010
0,0012
0,0014
0,0016
energy (eV)
100nm Fe
FWalteroptical_constants
Comparison with other experimentsComparison with other experiments
-7,5x10-3
-5,0x10-3
-2,5x10-3
0,0
2,5x10-3
B+ Bragg (Fe/C) B- Bragg (Fe/C) MOKE (100nm Fe)
Fe(
+/-
)
690 700 710 720 730 740
0,0
1,0x10-3
2,0x10-3
3,0x10-3
4,0x10-3
5,0x10-3
6,0x10-3
7,0x10-3
FWalterbragg
B+ Bragg (Fe/C) B- Bragg (Fe/C) MOKE (100nm Fe)
energy (eV)
Fe(
+/-
)
Comparison with other experimentsComparison with other experiments
-2,0x10-3
-1,0x10-3
0,0
1,0x10-3
2,0x10-3
FWalterbragg
Bragg (Fe/C) Faraday (Fe/C) Faraday (50 nmFe) MOKE (100nm Fe)
690 700 710 720 730 740
-2,0x10-3
-1,0x10-3
0,0
energy (eV)
Bragg (Fe/C) Faraday (Fe/C) Faraday (50nm Fe) KKT of MOKE (100nm Fe)
ConclusionConclusion
Exploiting tuneable synchrotron radiationExploiting tuneable synchrotron radiation
Obtaining optical constants for FeObtaining optical constants for Fe
New technique for obtaining optical New technique for obtaining optical constants in the soft x-ray regime for other constants in the soft x-ray regime for other materials such as Co, Ni, Gdmaterials such as Co, Ni, Gd