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http://hdl.handle.net/1843/38455| Type: | Dissertação |
| Title: | Growth temperature effects on the structural and magnetic properties of ferromagnetic nanostructures self-assembled on vicinal surface Ag(977) |
| Authors: | Matheus Felipe de Souza Barbosa |
| First Advisor: | Roberto Magalhães Paniago |
| First Referee: | Edmar Avellar Soares |
| Second Referee: | Luis Eugênio Fernandez Outon |
| Abstract: | The use of thin films, and more recently of nanostructures, to optimize physical and chemical properties of materials is ubiquitous nowadays. In this context, the deposition of ultrathin films on vicinal surfaces has been an area of great scientific curiosity, given that the periodic arrangement of substrate steps in nanometric scale can lead to the ordered growth of nanostructures, and such self-organization has great technological appeal. In particular, low dimensional ferromagnetic systems have received great attention due to promising applications in magnetic memory devices and spintronics. In order to improve the understanding of these systems, here we investigate the effects of the growth temperature on the structural and magnetic properties of ultrathin iron (Fe) and cobalt (Co) ferromagnetic films on vicinal Ag(977). A few monolayers (ML) were slowly deposited by molecular beam epitaxy (MBE) between 0.5 ML and 5.0 ML. In-situ analysis techniques were used, such as low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and magneto-optical Kerr effect (MOKE). For Fe/Ag(977) grown at room temperature, in the 2.0 ML to 5.0 ML range, we observe the formation of elongated nanostructures (“nanowires”) of Fe aligned with the step edges of the vicinal surface. At 500 K, between 1.0 ML and 3.0 ML, the growth of triangular structures was observed, most probably with surface alloy formation among the thin film and the substrate. For Co/Ag(977) samples grown at 500 K, for lower thickness, we observe the formation of triangular structures, suggesting Co stacking fault (FCC) on the Ag(111) terraces, and hexagonal structures due to Co-HCP stacking for higher thickness. From the point of view of magnetic properties, which were investigated by MOKE, we have observed from a thickness of 3.0 ML Fe on Ag(977) the presence of a distinguished ferromagnetic signal, when compared to the substrate diamagnetic signal. Nevertheless, for Co/Ag(977) a ferromagnetic signature was already present from 2.0 ML. Both systems have shown strong anisotropies and the experimental results indicate that the easy magnetization axis is in-plane and aligned with the steps, while the hard axis is out-of-plane. Furthermore, the coercive field strength has a dependence with the in-plane angle (φ) of the applied magnetic field, with a minimum value when aligned to the steps, which is in line with the nano-structured arrangement observed by STM. |
| Subject: | Matéria condensada Física de superfície Magnetismo |
| language: | eng |
| metadata.dc.publisher.country: | Brasil |
| Publisher: | Universidade Federal de Minas Gerais |
| Publisher Initials: | UFMG |
| metadata.dc.publisher.department: | ICX - DEPARTAMENTO DE FÍSICA |
| metadata.dc.publisher.program: | Programa de Pós-Graduação em Física |
| Rights: | Acesso Restrito |
| URI: | http://hdl.handle.net/1843/38455 |
| Issue Date: | 5-May-2021 |
| metadata.dc.description.embargo: | 5-May-2022 |
| Appears in Collections: | Dissertações de Mestrado |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| versao_final_dissertacao.pdf | Versão final dissertação | 14.39 MB | Adobe PDF | View/Open |
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