The general theme of the thesis is the interplay between magnetization dynamics and spin transport. The main presentation is divided into three parts. The first part is devoted to deepening our understanding on magnetic damping of ferromagnetic metals, which is one of the long-standing issues in conventional spintronics that has not been completely understood. For a nonuniformly-magnetized ferromagnetic metal, we find that the damping is nonlocal and is enhanced as compared to that in the uniform case. It is therefore necessary to generalize the conventional Landau-Lifshitz-Gilbert equation to include the additional damping. In a different vein, the decay mechanism of the uniform precession mode has been investigated. We point out the important role of spin-conserving electron-magnon interaction in the relaxation process by quantitatively examining its contribution to the ferromagnetic resonance linewidth. In the second part, a transport theory is developed for magnons which, in addition to conduction electrons, can also carry and propagate spin angular momentum via the magnon current. We demonstrate that the mutual conversion of magnon current and spin current may take place at magnetic interfaces. We also predict a novel magnon-mediated electric drag effect in a metal/magnetic-insulator/metal trilayer structure. This study may pave the way to the new area of insulator-based spintronics. In the third part of thesis, particular attention is paid to the influence the spin orbit coupling on both charge and spin transport. We theoretically investigate magnetotransport anisotropy and the conversion relations of spin and charge currents in various magnetic systems, and apply our results to interpret recent experiments.

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Submitted by Daniella Sodre (daniella.sodre@ufpe.br) on 2015-04-08T12:40:55Z No. of bitstreams: 2 DISSERTAÇÃO Gabriel Fonseca.pdf: 3837074 bytes, checksum: e2c9b20882785e374170658d648ee389 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-04-08T12:40:55Z (GMT). No. of bitstreams: 2 DISSERTAÇÃO Gabriel Fonseca.pdf: 3837074 bytes, checksum: e2c9b20882785e374170658d648ee389 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014-03-10 / Conselho Nacional de Desenvolvimento Científi co e Tecnol ógico; Coordenação de Aperfeiçoamento de Pessoal de Ní vel Superior; Financiadora de Estudos e Projetos; Fundação de Amparo a Ciência e Tecnologia do Estado de Pernambuco. / In this master thesis we study experimentally the longitudinal spin Seebeck effect (LSSE) in bilayers made of a ferromagnetic insulator (FMI) and a metallic layer (M). We also present a theoretical model based on the spin current density ⃗ Js carried by a non-equilibrium magnon distribution, generated by a thermal gradient ∇T across the thickness of the FMI. When ⃗ Js reach the FMI/M interface it is pumped towards the M layer due to conservation of the angular momentum, so, the M layer is essential for the LSSE existence. Here the FMI consists of a Yttrium Iron Garnet (YIG) lm, grown over a Gadolinium Gallium Garnet (GGG) substrate. Different metallic materials were used as the M layer i.e. Pt and Ta that have normal behavior and Py that is a ferromagnetic metal (FMM). The experimental procedure consists of systematic measurements of the electric voltage VISHE, produced by ⃗ Js through the Inverse Spin Hall Effect (ISHE) in the normal metal or (FMM) layer. In YIG/Pt measurements were done in the temperature range from 20 to 300 K. The experimental data are tted to the proposed model for the LSSE and good agreement is obtained. The results shows that the Py and Ta can be used to detect the LSSE with the ISHE. The results of this master thesis have strong interest in the area of spin caloritronics helping to the development of the eld and to raise possibilities of new spintronic devices. ----- Nesta diserta ção e estudado experimentalmente o Efeito Seebeck de Spin Longi- tudinal (LSSE), em bicamadas formadas por um isolante ferromagn etico (FMI) e um lme metalico (M). Tamb em foi desenvolvido um modelo te orico baseado na den- sidade de corrente de spin ⃗ Js que existe quando uma distribui c~ao de m agnons fora do equil brio e gerada por um gradiente t ermico ∇T aplicado na sec ção transversal do FMI. Quando ⃗ Js chega na interface FMI/M e bombeada para a camada M satis- fazendo a conserva ção do momentum angular, assim que a camada NM e essencial para ter um LSSE. Como camada FMI foi utilizada a granada de trio e ferro (YIG) crescida num substrato de (GGG). Diferentes materiais metalicos foram utilizados como camada M, sendo Pt e Ta paramagn eticos e o Py ferromagnetico. O proced- imento experimental consiste na medi c~ao sistem atica da voltagem el etrica VISHE, que e produzida por ⃗ Js por meio do efeito Hall de spin inverso (ISHE) que ocorre na camada M. As medidas em YIG/Pt foram feitas numa faixa ampla de temperatura de 20 a 300 K. Os dados experimentais são fi tados com a teoria proposta para o LSSE encontrando-se boa concordância. Nossos resultados mostram que o Py e o Ta s~ao bons candidatos para detec ção do LSSE. Esta disserta ção e de grande interesse na area da caloritrônica de spin, ajudando no desenvolvimento deste campo e na concep ção de novos dispositivos tecnol ogicos baseados na spintrônica.