1. Investigation of Magnetic Multilayer properties via
X-Ray Magnetic Circular Dichroism
By Emily Makoutz
Mentor: Hendrik Ohldag

2. STXM beamline at
SSRL BL13-1

3. From Fundamentals to Nanoscale Dynamics:
How are magnetic fields generated?
What makes a material magnetic?
How do we measure magnetization?

4. From Fundamentals to Nanoscale Dynamics:
1. Magneto Optical Kerr Effect (MOKE)
 A measure of total magnetization of a sample
2. X-ray Magnetic Circular Dichroism (XMCD)
3. Hysteresis Loops

5. Iris
Polarizer PhotodiodePower
Supply
Current
Amplifier
Computer
Interface
Laser HeNe
IrisPolarizer
Oscilloscope
Frequency
Generator
Mirror
Sample
MOKE
Experimental Setup
 Δ Magnetization of sample
 Δ Polarization upon reflection
 Δ Intensity
Δ Voltage
 Δ Current
 Δ External Magnetic Field
ΔV
ΔI
ΔVp
N
S

6. MOKE
Experiment and Results
Calibration curves
are used to convert
voltage to field
strength
Fe
MgO
-2 0 2
-0.4
-0.3
-0.2
-0.1
Topmost
Middle
Magnetic Test Sample
Intensity(arb.units)
Voltage (mV)

7. But…there are limitations
Fe
MgO

8. XMCD  Element Specific

9. XMCD  A measure of orbital momentum for
each elemental layer Tb and Co
𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 = 𝑒 𝜇𝑇 𝜇𝑇 ≡ 𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
1200 1250 1300
-0.2
0.0
0.2
0.4
uT
Energy (eV)
( - ) polarization
( + ) polarization
XMCD
760 800 840
0.0
0.2
0.4
( - ) Polarization
( + ) Polarization
XMCD Co
uT
Energy (eV)

10. MonochromatorUndulator
Polarizes
Light
e-
e-
e-
e-
A
SSRL
Selects a
Frequency A
A
XMCD
Experimental Setup
Gold Mesh Multilayer sample

11. XMCD  Hysteresis loops for Tb
-10 0 10
100000
120000
140000
I_diode
Voltage (V)
Id (+ / - )
Id (- / +)
From transmission From Electron Yield
-8 0 8
8
10
12
ElectronYield
Voltage (V)
EY(+ / -)
EY(- / +)

12. XMCD  Hysteresis loops for Tb
Circularly polarized vs Linearly Polarized
-8 0 8
8
10
12
14
ElectronYield
Voltage (V)
R-Circular (+ / -)
R-Circular (- / +)
Linear (+ / -)
Linear (- / +)

13. • MOKE allows us to probe bulk magnetization properites of a
sample with spatial resolution
• X-Rays allow us to evaluate magnetic properties of individual
layers of elements by evaluating absorbtion via
Photon in/Electron out
However, electron yield sign is distorted due the external
magnetic field
• Future work Develop Model to express electron yield as a
function of a modulating workfuntion
Summary

14. Acknowledgments and Thanks
Hendrik Ohldag
French Guys
SSRL
DOE
Enrique, Maria, and Corrine
And of course….
my fellow SULI/CCI folk