RessonÃncia ferromagnÃtica em vÃlvulas de spin e relaxaÃÃo em filmes de permalloy / RessonÃncia ferromagnÃtica em vÃlvulas de spin e relaxaÃÃo em filmes de permalloy

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

In this dissertation it has been investigated the dynamic properties of spin-valves and the relaxation mechanism in thin Permalloy films. All measurements reported here were obtained at room temperature, using a homemade ferromagnetic resonance (FMR) setup, working in the X-band regime of frequency. The spin-valve structures Si(001)/NiO(900Ã)/Py(100Ã)/Cu(tcu)/Py(100Ã)/Cu(45Ã) were prepared by dc magnetron sputtering. It has been investigate the dynamic properties of four samples with the Cu layer thickness changing from 0 Ã to 360Ã. It has been shown the exhistence of a competition between the indirect coupling, through the Py layers mediated by the Cu layer, with the direct coupling between the pinned Py layer and the NiO layer. The experimental results were interpreted by a phenomenological model which takes into account the magnetic free energy of the system. In order to investigated the relaxation processes in thin ferromagnetic films, we have prepared Permalloy samples with adjacents layers of the different materials. We show that the ferromagnetic resonance linewidth depends on the nature of the adjacent layer as well as the thickness of the permalloy layer. The Permalloy films that were deposited on top of Si(100) substrates exhibited a dependence with the Py layer thickness (t) that can be fitted as a function 1/t2. On the other hand, the Py films sandwiched by Pd, showed dependence with the Py layer thickness (t) that can be fitted as a function 1/t. These results show that different relaxation mechanisms are envolved. We also made a conection of our experimental results with the recently published theory of Arias and Mills

ASSUNTO(S)

mecanismos de relaxaÃÃo ferromagnÃtica espalhamento de dois-mÃgnons fisica exchange-bias estruturas de vÃlvulas de spin largura de linha de fmr ressonÃncia ferromagnÃtica (fmr)

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