masterThesis
Controle de paredes de domínio em nanoanéis de NiFe em estruturas núcleo-casca cilíndricas com acoplamento dipolar
Fecha
2017-01-25Registro en:
PESSOA, Nathan Lima. Controle de paredes de domínio em nanoanéis de NiFe em estruturas núcleo-casca cilíndricas com acoplamento dipolar. 2017. 77f. Dissertação (Mestrado em Física) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2017.
Autor
Pessoa, Nathan Lima
Resumen
Nanostructured magnetic systems and their properties have gone through
great achievement and still keep being focus of intense research effort nowadays.
From the pure theoretical point of view, the interest focus on new magnetic phases
that might emerge from dipolar effects in systems, with geometric constrictions,
with dimensions of the order of tenths of fundamental magnetic lengths. There is
also a large interest from the viewpoint of applications, such as magnetic sensors,
nano-oscillators and new designs of magnetic memories. Motivated by recent
experimental results, showing the possibility of domain wall confinement in ferromagnetic
nanorings, by magnetic constrictions like notches and asymmetries,
in addition to studies which reveal a strong impact of the domain wall width on
the electrical resistance, we propose a new form for creating and tailoring domain
walls in nanorings, by means of the magnetic dipolar interaction in cylindrical
core-shell nanostructures. In this work, we show that NiFe nanorings have their
magnetic pattern drastically changed when put in the presence of a coaxial Fe or
NiFe nanodisk. With a Fe nanodisk as the core, we have found the formation of
domain walls in NiFe nanorings that would hold magnetic vortices when isolated.
Furthermore, we show that large changes in the domain wall width and domain
wall patterns may be achieved by suitable choices of the core-shell geometrical
dimensions. For NiFe-NiFe core-shells, we have found that the core-shell dipolar
interaction affects both the core and shell phases, due to the vanishing anisotropy
of NiFe.