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