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  4. Helimagnons and Skyrmion Dynamics in Cu2OSeO3 and Fe/Gd Multilayers Explored by Brillouin Light Scattering and X-ray Microscopy
 
doctoral thesis

Helimagnons and Skyrmion Dynamics in Cu2OSeO3 and Fe/Gd Multilayers Explored by Brillouin Light Scattering and X-ray Microscopy

Che, Ping  
2021

Spin dynamics in skyrmion hosting materials provide novel functionality in magnonics because of the formation of a novel magnon band structure and the nanoscale sizes of magnetic skyrmions. In this thesis, we explore the spin dynamics in the chiral magnet Cu2OSeO3 locally utilizing the scanning micro-focus Brillouin light scattering (BLS) technique at cryogenic temperature. Taking advantage of the high sensitivity and spatial resolution of BLS, we resolved the one-to-one correspondence between different non-collinear phases, such as helical, chiral soliton, conical and skyrmion phases, in a chiral magnet and their collective spin excitations. We show that the continuous-wave laser in BLS enables the stabilization of metastable phases and creation of skyrmion tracks surrounded by the conical phase. The high sensitivity of BLS allows us to deepen the understanding of coexisting phases in the chiral magnet. The results pave the way for the design of further magnonic devices based on chiral magnets. Furthermore, we explore dipolar skyrmions and domain walls in amorphous Fe/Gd multilayers employing scanning transmission x-ray microscopy. We demonstrate the formation of stripe and square lattices of domains by integrating one-dimensional and two-dimensional nanomagnet arrays, respectively. Dynamics of domain walls, multi-domain boundaries and skyrmions were captured with pump-probe spectroscopy. In a skyrmion pair, a magnon wavelength down to 239 nm at 0.33 GHz was observed and compared to the electromagnetic wave whose wavelength is 0.9 m at the same frequency. The extreme wavelength conversion underlines the potential of skyrmion hosting materials concerning miniaturization of information technology and microwave devices.

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Type
doctoral thesis
DOI
10.5075/epfl-thesis-8280
Author(s)
Che, Ping  
Advisors
Grundler, Dirk  
Jury

Prof. Oleg Yazyev (président) ; Prof. Dirk Grundler (directeur de thèse) ; Prof. Jean-Philippe Ansermet, Prof. Geoffrey S.D. Beach, Prof. Sergej Demokritov (rapporteurs)

Date Issued

2021

Publisher

EPFL

Publisher place

Lausanne

Public defense year

2021-08-26

Thesis number

8280

Total of pages

183

Subjects

spin dynamics

•

magnon

•

magnetic skyrmions

•

domain walls

•

chiral magnet

•

perpendicular magnetic anisotropy

•

Brillouin light scattering

•

scanning transmission x-ray microscopy

EPFL units
LMGN  
Faculty
STI  
School
IMX  
Doctoral School
EDPY  
Available on Infoscience
August 20, 2021
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/180741
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