Datum
2022Autor
Reginka, MeikeSchlagwort
530 Physik MagnetwerkstoffTexturDünne SchichtSiliciumMikrostrukturWirbel <Physik>Magnetische EigenschaftArrayMetadata
Zur Langanzeige
Dissertation
Magnetic Textures and Magnetization Reversal Processes in Arrays of Ferromagnetic and Exchange-Biased Hollow Hemispheres
Zusammenfassung
The main objective of this thesis is to investigate hemispherical caps prepared by thin film deposition of magnetic material compositions on top of nano- and micrometer sized silica spheres. When compared to flat magnetic discs, these microcaps differ in their magnetic properties due to the curved and therefore three-dimensional shape. However, under certain conditions, both microstructures have previously been proven to express the famous magnetic vortex texture because of the confinement into a circular shape. Vortices, in which the magnetic moments curl around the object’s center, are not only fundamentally studied to this day but are also traded as potential information carriers in spintronic devices. Aside of purely ferromagnetic caps, the focus of this thesis lies on cap structures exhibiting an exchange bias (EB). This effect emerges as an additional unidirectional magnetic anisotropy due to exchange coupling when a thin antiferromagnetic and ferromagnetic material share an interface. While it is aimed to study whether the effect’s characteristics known from flat bilayers are influenced when the film is structured into an array of curved microobjects, it shall also be investigated how the remagnetization of the caps - including the passing through various characteristic magnetization textures - is altered by the presence of EB. Throughout the work, the structural and magnetic properties of assembled magnetic cap arrays are experimentally studied to identify methods to tailor the exhibition of specific magnetic textures and remagnetization paths: e.g., the cap’s diameter, the ferromagnetic material, the presence or absence of EB, and post-deposition treatments. But most importantly, the caps’ magnetization reversal is studied in dependence on the ferromagnetic thickness which turned out to be a key parameter influencing both the EB strength and the demagnetization energy of the magnetic states expressed within the microcaps. Last but not least, it is found that the thickness of the antiferromagnetic layer determines whether the macroscopic magnetization reversal of the caps follows a biased, i.e., simply shifted hysteresis, or whether they remagnetize viscously instead.
Sammlung(en)
Dissertationen (Experimentalphysik IV - Funktionale dünne Schichten & Physik mit Synchrotronstrahlung)Zitieren
@phdthesis{doi:10.17170/kobra-202212237262,
author={Reginka, Meike},
title={Magnetic Textures and Magnetization Reversal Processes in Arrays of Ferromagnetic and Exchange-Biased Hollow Hemispheres},
school={Kassel, Universität Kassel, Fachbereich Mathematik und Naturwissenschaften, Institut für Physik},
year={2022}
}
0500 Oax 0501 Text $btxt$2rdacontent 0502 Computermedien $bc$2rdacarrier 1100 2022$n2022 1500 1/eng 2050 ##0##http://hdl.handle.net/123456789/14382 3000 Reginka, Meike 4000 Magnetic Textures and Magnetization Reversal Processes in Arrays of Ferromagnetic and Exchange-Biased Hollow Hemispheres / Reginka, Meike 4030 4060 Online-Ressource 4085 ##0##=u http://nbn-resolving.de/http://hdl.handle.net/123456789/14382=x R 4204 \$dDissertation 4170 5550 {{Magnetwerkstoff}} 5550 {{Textur}} 5550 {{Dünne Schicht}} 5550 {{Silicium}} 5550 {{Mikrostruktur}} 5550 {{Wirbel <Physik>}} 5550 {{Magnetische Eigenschaft}} 5550 {{Array}} 7136 ##0##http://hdl.handle.net/123456789/14382
2023-01-23T10:37:22Z 2023-01-23T10:37:22Z 2022 doi:10.17170/kobra-202212237262 http://hdl.handle.net/123456789/14382 eng Namensnennung - Nicht-kommerziell - Weitergabe unter gleichen Bedingungen 4.0 International http://creativecommons.org/licenses/by-nc-sa/4.0/ 530 Magnetic Textures and Magnetization Reversal Processes in Arrays of Ferromagnetic and Exchange-Biased Hollow Hemispheres Dissertation The main objective of this thesis is to investigate hemispherical caps prepared by thin film deposition of magnetic material compositions on top of nano- and micrometer sized silica spheres. When compared to flat magnetic discs, these microcaps differ in their magnetic properties due to the curved and therefore three-dimensional shape. However, under certain conditions, both microstructures have previously been proven to express the famous magnetic vortex texture because of the confinement into a circular shape. Vortices, in which the magnetic moments curl around the object’s center, are not only fundamentally studied to this day but are also traded as potential information carriers in spintronic devices. Aside of purely ferromagnetic caps, the focus of this thesis lies on cap structures exhibiting an exchange bias (EB). This effect emerges as an additional unidirectional magnetic anisotropy due to exchange coupling when a thin antiferromagnetic and ferromagnetic material share an interface. While it is aimed to study whether the effect’s characteristics known from flat bilayers are influenced when the film is structured into an array of curved microobjects, it shall also be investigated how the remagnetization of the caps - including the passing through various characteristic magnetization textures - is altered by the presence of EB. Throughout the work, the structural and magnetic properties of assembled magnetic cap arrays are experimentally studied to identify methods to tailor the exhibition of specific magnetic textures and remagnetization paths: e.g., the cap’s diameter, the ferromagnetic material, the presence or absence of EB, and post-deposition treatments. But most importantly, the caps’ magnetization reversal is studied in dependence on the ferromagnetic thickness which turned out to be a key parameter influencing both the EB strength and the demagnetization energy of the magnetic states expressed within the microcaps. Last but not least, it is found that the thickness of the antiferromagnetic layer determines whether the macroscopic magnetization reversal of the caps follows a biased, i.e., simply shifted hysteresis, or whether they remagnetize viscously instead. open access Reginka, Meike 2022-10-25 ix, 172 Seiten Kassel, Universität Kassel, Fachbereich Mathematik und Naturwissenschaften, Institut für Physik Ehresmann, Arno (Prof. Dr.) Albrecht, Manfred (Prof. Dr.) Giesen, Thomas (Prof. Dr.) Pastor, Gustavo Miguel (Prof. Dr.) Magnetwerkstoff Textur Dünne Schicht Silicium Mikrostruktur Wirbel <Physik> Magnetische Eigenschaft Array publishedVersion false true
Die folgenden Lizenzbestimmungen sind mit dieser Ressource verbunden: