Banca de DEFESA: ACÁCIO SILVEIRA DE MELO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : ACÁCIO SILVEIRA DE MELO
DATA : 23/03/2017
HORA: 14:00
LOCAL: Auditório do DFTE
TÍTULO:

Meander-line Multilayer Magnetoimpedance: Magnetization dynamics in ferromagnetic trilayers

PALAVRAS-CHAVES:

Magnetization dynamics, Thin films, Meander-line, magnetic anisotropy.

PÁGINAS: 103
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
RESUMO:

The magnetoimpedance effect (MI) is an interesting tool for a completely analysis of the magnetic nanostructures, since is possible to observe the magnetization dynamics behavior at a wide range of frequency and external magnetic field,  in both saturated and unsaturated regimes.  In the last years studies about the MI effect as a function of sample geometry has been performed. In particular in trilayer systems and meander-lines samples, separately.  Based on this, here we seeks the integration  between these two geometry (trilayer and meander-line) and the structural and magnetic properties (quasi-static and dynamics) are explored in [NiFe/Cr/NiFe] trilayered samples. The samples were produced by Magnetron Sputtering technique under glass amorphous substrate with thicknesses of 75 - 142.5 nm for the ferromagnetic layer and 15-150 nm for the Cr layer, totalizing 10 samples. However, the total thicknesses of the trilayered samples are remained constant of 300 nm, irrespectively of the produced sample. Associated with this, for each set of thicknesses three in-plane substrate geometry were explored. The first one, a rectangular geometry, traditionally studied, the last two a meander-line geometry are studied. In particular, to reach these geometry for the samples, masks were used during the deposition process.  The structural characterization, trough X-ray diffraction, shows a crystalline behavior with a [111] texture, usually found for NiFe thin films grown onto amorphous substrate. The quasi-static characterization was performed through magnetization curves, obtained from a Vibrating Sample Magnetometer (VSM), with external magnetic field applied in the film-plane for distinct direction with respect to the mains axis of the samples, to verify the anisotropy behavior. In a general point of view, the magnetization curves reveal the isotropic behavior in the film-plane and a strongly dependence with the NiFe thicknesses.  On the other hand, a weak dependence with the sample geometry (rectangular or meander-line) is observed, as expected. Finally, for the magnetization dynamics study the magnetoimpedance effect was used in a wide range of field ( 700 Oe) and frequency (0.5 up to 3.0 GHz). Besides, two field configuration between the external magnetic field and the drive current were explored, named by longitudinal and transverse measurements. The MI measurements present a double or multiple peaks structures, characteristic of the FMR contribution in the MI variations in this frequency range. With respect to the MI effect dependence,  as a function of the thicknesses ratio of the NiFe and Cr layers,  is possible to observe a strongly influence of the out-of-plane magnetic anisotropy in the peaks structures in the MI curves, mainly for the samples with thick NiFe layer.  Lastly, the MI curves as a function of the sample geometry reveal changes in the dynamics magnetization, carrying asymmetric MI curves and a complexity in the peak structure.

MEMBROS DA BANCA:
Presidente - 1474380 - MARCIO ASSOLIN CORREA
Interno - 2195232 - TOMMASO MACRI
Externo à Instituição - ANTÔNIO MARCOS HELGUEIRA DE ANDRADE - UFRGS