Banca de DEFESA: EDIMILSON FELIX DA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : EDIMILSON FELIX DA SILVA
DATA : 12/08/2016
HORA: 14:00
LOCAL: Auditório do DFTE
TÍTULO:

Quasi-static and dynamic magnetic properties of biphase ferromagnetic films

PALAVRAS-CHAVES:

Magnetization dynamics, Thin films, Assymmetric magnetoimpedance effect, Interlayer interactions

PÁGINAS: 160
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
ESPECIALIDADE: Materiais Magnéticos e Propriedades Magnéticas
RESUMO:

The magnetoimpedance effect appears as one of the most versatile tools to investigate nanostructured magnetic materials, revealing its magnetic properties in different frequency ranges and magnetic field values, even at unsaturated states. In recent decades, great attention has been given to this effect due to their contribution to the understanding of the physics associated to the magnetization dynamics and to the possibility of application of magnetic materials as probe element in sensor devices for low-field detection. Although soft magnetic materials are highly sensitive to small variations in low magnetic fields, many of them have essentially a nonlinear magnetoimpedance behavior in magnetic fields near zero, which prevents a simple straightforward derivation of an appropriate signal for sensors applications. To improve the linear features of the magnetoimpedance response, several studies have been carried out considering different magnetic systems, including wires, ribbons and amorphous multilayered films with \textit{exchange bias}. Recently, it has been shown that materials exhibiting asymmetric magnetoimpedance, characterized by a linear response close to zero magnetic field, appear as a promising alternative for applications, opening the possibility to use such materials in auto-biased linear magnetic field sensors. In these materials, asymmetric effects are obtained by inducing asymmetric static magnetic configuration, usually done by magnetostatic interactions, exchange bias, or by modifying the orientation of the external magnetic field and magnetic anisotropy.

In this work, we investigate the structural properties, quasi-static magnetic properties, and the magnetization dynamics and magnetoimpedance effect in biphase ferromagnetic films and multilayers, with structures NiFe/NM/Co, where NM is a non-magnetic metallic spacer. Considering the results, these films present biphase magnetic behavior and asymmetric magnetoimpedance effect. We observe that the magnetoimpedance response is dependent on the thickness of the non-magnetic spacer material, explore the possibility of tuning the linear region of the magnetoimpedance curves around zero magnetic field by varying the thickness of the spacer and probe current frequency, and optimize the sensitivy by considering multilayered films. We discuss the experimental results in terms of the different mechanisms governing the magnetization dynamics at distinct frequency ranges, quasi-static magnetic properties, thickness of the spacer, and the kind of the magnetic interaction between the ferromagnetic layers. The results place films with biphase magnetic behavior exhibiting asymmetric magnetoimpedance effect as very attractive candidates for application as probe element in the development of auto-biased linear magnetic field sensors.

MEMBROS DA BANCA:
Presidente - 1508681 - FELIPE BOHN
Interno - 1457464 - LUIZ FELIPE CAVALCANTI PEREIRA
Interno - 1474380 - MARCIO ASSOLIN CORREA
Externo à Instituição - ANTONIO AZEVEDO DA COSTA - UFPE
Externo à Instituição - RUBEM LUÍS SOMMER - CBPF