PhD Defense: Txema Porro, on 07.02.2014 at 11:00
CIC nanoGUNE Seminars
- Speaker
-
Txema Porro (Nanomagnetism Group)
- When
-
2014/02/07
12:00 - Place
- Korta Building
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**Title** : " Exploiting magnetic dipolar interactions in artificially
nanostructured systems "
**Thesis supervisor** : Paolo Vavassori
_When_ : 7 February, Friday, 11:00
**Where** : Korta Building
**Abstract** :
This PhD thesis deals with the study of magnetic dipolar interactions in
different ferromagnetic nanostructured materials. After an introduction to
ferromagnetism at the nanoscale, the nanofabrication method used to pattern
the nanostructures issue of study in this thesis is presented. By means of
Electron-Beam Lithography, well-defined ferromagnetic nanostructures with
sub-50nm gaps between neighbouring nanoelements have been fabricated in a
fully controlled and reproducible fashion. After that, three different cases
where magnetic dipolar interactions play a predominant role are presented. The
first case consists in studying the magnetization reversal process in
elongated ferromagnetic nanoelements coupled through asymmetric dipolar
interactions, due to which it is possible to tune the magnetization reversal
pathway. Depending on the orientation of the externally applied field it is
possible to induce the formation of stable non-uniform magnetization states at
remanence in nanomagnets where these non-uniform states are energetically
extremely unfavoured with respect to a single-domain state. The second case
consists of studying the physics of the accommodation of frustration in so-
called Artificial Spin-Ice nanostructures. Different demagnetization protocols
have been proposed in literature to study how the magnetization of the
nanoelements is accommodated. In this thesis a thermal demagnetization
protocol never reported previously in literature is presented: with this
demagnetization protocol systematic studies of the accommodation of
frustration in Artificial Spin-Ice samples become possible. The third case
deals with the study of the effect of ultrafast dipolar magnetic field pulses,
created by the displacement of a domain wall through a nanostripe, on the
magnetization of adjacent magnetic nanoellipses placed at a distance of 50nm
from the nanostripe. A magnetization reversal process in these nanoellipses is
induced, provoked by the action of the ultrafast magnetic field pulse created
by the domain wall being displaced through the nanostripe.