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!