Download - Final Presentation Traineeship T Ue
![Page 1: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/1.jpg)
Imaging of domain walls in small shape anisotropy dominated magnetic structures
Internal Traineeship - Michael Beljaars
![Page 2: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/2.jpg)
Outline
Introduction Magnetic Force Microscopy Magnetic Tips Domain imaging Conclusion
![Page 3: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/3.jpg)
Introduction
Motivationmaking fast current switchable magnetic memory (MRAM)
Methodswitching magnetization through domain wall propagation
Intr
oduc
tion
![Page 4: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/4.jpg)
MRAM
Conventional switching with applied magnetic field
Intr
oduc
tion
fixed magnetic layer
insulating barier
switching magnetic layer
applied field applied field
Resistance of the stack depends on magnetization direction of the switching layer
magnetization direction
![Page 5: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/5.jpg)
MRAM
Switching with domain wall propagation
current pulse
domain wall
Intr
oduc
tion
Spin torque effect
![Page 6: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/6.jpg)
Domain wall propagation
Physical Review Letters, Vo. 92, No.7 077205-1 Intr
oduc
tion
![Page 7: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/7.jpg)
Why single domain?
Multi domain means multiple domain walls. Propagation becomes unpredictable.
Uniform magnetization necessary for MTJ: switching between two domains
multiple domain walls single domain wall
Intr
oduc
tion
![Page 8: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/8.jpg)
Roadmap
Create a single domain structure Induce a domain wall by means of a
external field Propagate the domain wall with current
pulses Integrate the structure with a Magnetic
Tunnel Junction (MTJ)
Intr
oduc
tion
![Page 9: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/9.jpg)
Magnetic Force Microscopy
AC MFM First pass: topography Second pass:
magnetic force gradient
Mag
netic
For
ce M
icro
scop
y
![Page 10: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/10.jpg)
Harmonic oscillator
0
00
F k z
k
mω
= −
=
0
0
00
0
'
''
1 1' '
' '
m
m
m m
dFk k
dz
dFkk dz
m m
k dF dF
m m dz m dz
ω
ω ω
ω ω
= +
+= =
= + = +
= +
Free vibration Additional force
Mag
netic
For
ce M
icro
scop
y
![Page 11: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/11.jpg)
0
0
2
3 3
1
2
m
m
m
dFQ
k dz
A Q dFA
dzk
dF
k dz
ϕ
ω ω
∆ ≈
∆ ≈
∆ ≈ −
Mag
netic
For
ce M
icro
scop
y
![Page 12: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/12.jpg)
Magnetic Tips
Nanoworld tips (bought at Nanoworld.com)
Mag
netic
Tip
s –
Nan
owor
ld T
ips
![Page 13: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/13.jpg)
Nanoworld Tips
topographic image magnetic image
Mag
netic
Tip
s –
Nan
owor
ld T
ips
![Page 14: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/14.jpg)
Applying a magnetic field
Mag
netic
Tip
s –
Nan
owor
ld T
ips
![Page 15: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/15.jpg)
Field dependence
5000 0
100 50
10 025 gauss
Field
Mag
netic
Tip
s –
Nan
owor
ld T
ips
![Page 16: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/16.jpg)
One line profile
0 gauss
50 gauss
Signal weakens dramatically
4 deg
1 deg
Mag
netic
Tip
s –
Nan
owor
ld T
ips
![Page 17: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/17.jpg)
Explanation
Damage breaks shape anisotropy
Magnetization rotates due to the applied field
Mag
netic
Tip
s –
Nan
owor
ld T
ips
![Page 18: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/18.jpg)
Magnetic Tips
Sputtered tips (contact tips from NT-MDT)
Mag
netic
Tip
s –
Spu
ttere
d T
ips
![Page 19: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/19.jpg)
Sputtered Tips
Mag
netic
Tip
s –
Spu
ttere
d T
ips
![Page 20: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/20.jpg)
Advantages
Smaller magnetic moment due to partial coating of the tip, less influencing the sample
More local interaction, leading to a higher spatial resolution
Mag
netic
Tip
s –
Spu
ttere
d T
ips
![Page 21: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/21.jpg)
Harddisk
topographic image magnetic image
Mag
netic
Tip
s –
Spu
ttere
d T
ips
![Page 22: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/22.jpg)
Comparison
Nanoworld tips Sputtered tips
Contrast enhancement
Higher resolution
Mag
netic
Tip
s
![Page 23: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/23.jpg)
Conclusions on sputtered tips
Better resolution due to smaller area of interaction
Opportunities for new research to understand the behaviour of these tips and optimise the characteristics (material, layer thickness)
![Page 24: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/24.jpg)
Domain Imaging
Dom
ain
imag
ing
![Page 25: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/25.jpg)
E-beam sample I
Dom
ain
imag
ing
![Page 26: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/26.jpg)
First MFM scan
topographic image magnetic image
multi domain
Dom
ain
imag
ing
~1500 nm
![Page 27: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/27.jpg)
Domain structure at different fields
150 gauss
Dom
ain
imag
ing
160 gauss 170 gauss 0 gauss
0 gauss 50 gauss 75 gauss 100 gauss
direction of the field
![Page 28: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/28.jpg)
E-beam sample II
0,5
μm
0,1 μ
m
0,2 μ
m
1 μm
Dom
ain
imag
ing
![Page 29: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/29.jpg)
Microscope photographs
Dom
ain
imag
ing
structure 1 structure 2 structure 3
structure 4 structure 5 structure 6
Dimension:~55 x 55 μm
Typical width:~1 μm
![Page 30: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/30.jpg)
Microscope photographs
Dimension:23 x 23 μmTypical width:800 – 900 nm
Dimension:27 x 27 μmTypical width:900 – 1000 nm
single domainexpected
![Page 31: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/31.jpg)
Single domain?
topographic image magnetic image
~1
100
nm
![Page 32: Final Presentation Traineeship T Ue](https://reader034.vdocuments.site/reader034/viewer/2022042615/55adf94e1a28ab8f5f8b46fc/html5/thumbnails/32.jpg)
Conclusion
Great advantage Single domain for 1 μm or smaller