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Título
Advanced modelling of domain wall dynamics for spintronic devices
Autor(es)
Director(es)
Materia
Tesis y disertaciones académicas
Universidad de Salamanca (España)
Academic dissertations
Tesis doctoral
Magnetism
Magnetismo
Espintrónica
Fecha de publicación
2017-11
Resumen
[EN]The study of magnetism at the nanoscale has important applications in everyday
life. As an example, the vast majority of all data is currently stored in magnetic hard
drives, while magnetic sensors are ubiquitous in automotive applications and in the
internet of things (IoT) technology. The interaction between the spins of conducting
electrons and those of the localized magnetic moments of a ferromagnet is at the
base of a new field of studies called Spintronics, whose technological perspectives
are to overcome the existing semiconductor technology in terms of power saving,
endurance and reliability.
Domain wall propagation is the mechanism through which a magnetic system
changes its state when its equilibrium is perturbed via an external action and its
dynamics is well described using the micromagnetic formalism. Micromagnetic nu-
merical simulations are a proficient tool that links experimental observations and
theoretical predictions, leading the way in the theoretical understanding of magne-
tization dynamics and domain wall motion.
In chapter 1 we lay down the fundamental physical concepts of the micromag-
netic description of magnetism and present the principal analytical tools used through-
out the the rest of the work. Chapter 2 is dedicated to the description of the nu-
merical solver used in this work: a custom micromagnetic code based on C++ and
CUDA programming languages, developed within the group. Subsequently, we fo-
cus on two different problems, making use of the descriptive and predictive power
of micromagnetic simulations respectively.
In chapter 3, we investigate the effect of disorder on field driven domain wall
dynamics in CoFeB thin films. Such structures are the building blocks of MRAM
memories and the understanding of field driven domain wall dynamics is a key
step towards the optimization of device functionality. Exploiting the ability of mi-
cromagnetic simulations to reproduce certain disorder features realistically, we get
insight into magnetization dynamics taking place at a scale below instruments reso-
lution, uncovering important connections between domain wall dynamics and ma-
terial disorder features. Disorder triggers internal domain wall dynamics that gen-
erates a faster energy dissipation and a faster domain wall propagation in the high-
field regime.
In chapter 4, we propose a new spintronic device based on the emission of spin
waves by means of the controlled rotation of a domain wall in a ferromagnetic wire.
The transmission of information via the periodic oscillatory perturbation of mag-
netization, called spin wave, offers new perspectives in the design of low power
sensors and emitters. We design a system with realistic material characteristics and
investigate how the self oscillatory state of a domain wall, induced by the injection
of a charge current, can emit a spin wave signal at frequency of tens of GHz that
directly depends on the injected current intensity.
URI
DOI
10.14201/gredos.137343
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