Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Magnetic dynamics of periodic and quasiperiodic
arrays of NiFe stripes
Filip Lisiecki
Plan of presentation
• Introduction
• Subject of study and used methods
• Results
• Summary
2
3
Introduction
Motivation
4
Electronic Spintronic
Information carrier:
electron charge
Information carrier:
electron spin
jc js
GMR (Nobel Prize in 2007)
TMR
STT
…
Magnonic
Information carrier:
magnon
*
*(c) A. V. Chumak, TU Kaiserslautern
Motivation
5
• Information carriers: magnons
(no electron flow, low energy
consumption)
• High operational frequency
(GHz, THz)
• Better miniaturization in
comparison to photonic
devices
• Integration with microwave
photonic and electronic devices
• Information as amplitude or
phase (parallel data
processing)
• Communication, processing and storage of information
Motivation
6
Logic gates Magnonic transistor
8mm1.5mm
A. V. Chumak et al., Nat. Commun. 2014
A. Khitun et al., J. Phys. D: Appl. Phys. 2010
Currently realization of these kind of devices based on YIG in mm scale
𝑀 - magnetization
𝐻𝑒𝑓𝑓 - effective magnetic
field
𝛾 –gyromagnetic ratio
7
Magnetization precession
1
𝛾
𝑑𝑀
𝑑𝑡= −𝑀(t) × 𝐻𝑒𝑓𝑓(𝑡)
+𝛼
𝑀𝑀 ×𝑑𝑀
𝑑𝑡
𝛼 – damping coefficient
(Gilbert)
Landau-Lifshitz equation
*(c) D. Bozhko, AG Hillebrands, TU Kaiserslautern
*
• Collective spins excitation
• Magnon - quasiparticle
• Energy
• Quasimomentum
• Mass
• Wave effects
• Much shorter wavelength
in comparison with
electromagnetic wave
8
Spin waves
𝜀 = ℏ𝜔
𝑝 = ℏ𝑘𝜆𝑘
*(c) D. Bozhko, AG Hillebrands, TU Kaiserslautern
*
• Harmonic or pulsed magnetic field
• Ultrashort optical impulses
• Spin polarized current
• Coplanar waveguide (CPW)
[5]
9
Spin waves excitation
BLS spectroscopy
Microstrip antenna
*(c) D. Bozhko, AG Hillebrands, TU Kaiserslautern
*
10
Magnonic crystals
a
*(c) A. Chumak, TU Kaiserslautern
*
*
11
Magnonic crystals
V. L. Zhang et al., APL 2011
• Stripes array: Co(200 nm)/Py(300 nm)
H = 37 mT/μ0
12
Subject of studyand used methods
• Fibonacci:
quasiperiodic
structure
• 𝐹𝑛 = 𝐹𝑛−1 + 𝐹𝑛−2• A: 350 nm Py
(Ni80Fe20)
• B: 100 nm air
• Thickness 30 nm
13
Fibonacci and periodic stripes array
• Poorly known in the literature
• Stripes of Co and Py (UAM)
• Rich spin waves spectra
14
Fibonacci stripes array
J. Rychły et al., PRB 2015
Fibonacci periodic
IDOS(fi) =
j=0
i
DOS fj
15
Lithography process and lift-off
16
Periodic and quasiperiodicstructures
Width: 349 nm Width: 352 nm (narrow)695 nm (wide)Permalloy
• 𝛼 = 0.008
• technological reasons
17
Si
antenna
VNA-FMR antenna
G S G
Py
structures
Vector network analyzer (VNA)
• Spin excitation with magnetic field around coplanar
waveguide (CPW) lines
• Frequency sweeping 2 GHz – 13 GHz
• H = const (-440 to +440 Oe)
• Ferromagnetic resonance in relation to frequency
and magnetic field
Probe tips
T. Schwarze, PhD
Thesis, TUM 2013
Hext
18
VNA-FMR measurements
19
VNA-FMR measurements
k
Hext
hrf
Results
20
21
Fibonacci structure
VNA-FMR
22
Periodic structure
VNA-FMR
Fibonacci structure
L-MOKE (UwB), minor loops
1
2
3
23
24
Fibonacci structureVNA-FMR, MFM (UwB), minor loops
Hmin=-147 Oe1
Hmin=-99 Oe2
25
Fibonacci structureVNA-FMR, MFM (UwB), minor loops
Hmin=-67 Oe3
Periodic structure
L-MOKE (UwB), minor loops
1
2
3
4
5
26
27
Periodic structureVNA-FMR, MFM (UwB), minor loops
Hmin=-177 Oe Hmin=-144 Oe1 2
28
Periodic structureVNA-FMR, MFM (UwB), minor loops
Hmin=-111 Oe Hmin=-88 Oe3 4
29
Periodic structureVNA-FMR, MFM (UwB), minor loops
Hmin=-55 Oe5
Magnetization switching in stripes
30
Periodic Fibonacci
Magnetization switching in stripes
31
-350 -300 -250 -200 -150 -100 -50
-1,0
-0,5
0,0
0,5
1,0
M
/Ms
Field (Oe)
Periodic_5um_{xy}
Fibonacci_5um_{xy}
Simulations (M. Zelent - UAM)
Simulations (UAM)
• Periodic
• Fibonacci
32
Magnetization switching in stripes
Magnetization switching in stripes
• g = 0.76 μm, 1.50 μm,
10 μm, ∞ (single)
• s = 5 or 10 μm
• thickness: 30 or 50 nm
33
-400 -300 -200 -100 0 100 200 300 400-1,2
-1,0
-0,8
-0,6
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
M/M
s
Field (Oe)
Fibo 5um, 30nm, single
Per 5um, 30nm, single
-400 -300 -200 -100 0 100 200 300 400-1,2
-1,0
-0,8
-0,6
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
M/M
s
Field (Oe)
Fibo 5um, 30nm, 0.76um
Per 5um, 30nm, 0.76um
L-MOKE (UwB)
Fibo/Per 5μm, 30nm, single Fibo/Per 5 μm, 30nm, gap 0.76 μm
Magnetization switching in stripes
34
Magnetization switching in stripes
Periodic
Fibonacci
-400 -300 -200 -100 0 100 200 300 400-1,2
-1,0
-0,8
-0,6
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
M/M
s
Field (Oe)
Fibo 5um, 50nm, single
Fibo 5um, 50nm, 10um
Fibo 5um, 50nm, 1.5um
Fibo 5um, 50nm, 0.76um
L-MOKE (UwB)
Magnetization switching in stripes
Magnetization switching in stripes
-400 -300 -200 -100 0 100 200 300 400-1,2
-1,0
-0,8
-0,6
-0,4
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
M/M
s
Field (Oe)
Fibo 5um, 50nm, single
Fibo 5um, 50nm, 10um
Fibo 5um, 50nm, 1.5um
Fibo 5um, 50nm, 0.76um
L-MOKE (UwB)
Fibo 5um, 30nm, gap 1.5um Per 5um, 30nm, gap 1.5um
No clear switching pattern (defects?).
Magnetization switching in stripes
• Periodic structures: visible acoustic mode, anti-parallel
configuration in MFM images and VNA-FMR spectra was observed
• Quasiperiodic structures: two coercive fields connected with
magnetization switching in stripes of different width (700 nm in
lower and 350 nm in higher fields), in VNA-FMR spectra acoustic
mode and additional, connected mostly with narrow stripes were
observed
• Different plateau slope in hysteresis loops for quasiperiodic and
periodic structures
• Reducing the gap between stripes array decreases interaction
between nanostripes
• Pattern in magnetization switching seen in simulations not
observed in experiment (defects?)
39
Summary
[1] A. V. Chumak, A. A. Serga, and B. Hillebrands, “Magnon
transistor for all-magnon data processing,” Nat. Commun., vol. 5, p.
4700, Aug. 2014.
[2] J. Ding, M. Kostylev, and A. O. Adeyeye, “Magnetic
hysteresis of dynamic response of one-dimensional magnonic
crystals consisting of homogenous and alternating width nanowires
observed with broadband ferromagnetic resonance,” Phys. Rev. B,
vol. 84, no. 5, Aug. 2011.
[3] V. V. Kruglyak, S. O. Demokritov, and D. Grundler,
“Magnonics,” J. Phys. Appl. Phys., vol. 43, no. 26, p. 264001, 2010.
[4] M. Krawczyk and D. Grundler, “Review and prospects of
magnonic crystals and devices with reprogrammable band
structure,” J. Phys. Condens. Matter, vol. 26, no. 12, p. 123202, Mar.
2014.
40
Bibliography
41
Piotr Kuświk
Hubert Głowiński
Michał Matczak
Janusz Dubowik
Feliks Stobiecki
Piotr MazalskiAndrzej Maziewski
Justyna Rychły
Mateusz ZelentMaciej Krawczyk
42
Thank you!