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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Estudo experimental de sistemas frustrados e dispositivos híbridos para aplicações em altas e baixas frequências / Experimental study of frustrated systems and hybrid devices for high and low frequency applications

Ribeiro, Igor Renato Bueno 22 June 2017 (has links)
Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-10-26T12:14:20Z No. of bitstreams: 1 texto completo.pdf: 4645099 bytes, checksum: 2a149d2cab06b6267f00ebb89d37b1cf (MD5) / Made available in DSpace on 2017-10-26T12:14:20Z (GMT). No. of bitstreams: 1 texto completo.pdf: 4645099 bytes, checksum: 2a149d2cab06b6267f00ebb89d37b1cf (MD5) Previous issue date: 2017-06-22 / Nesta tese foram fabricados e caracterizados três sistemas: o gelo de spin artificial (GSA), o Anti-GSA e um tipo de dispositivo híbrido. O primeiro, GSA, consiste de uma distribuição de nanoilhas ferromagnéticas (300nm x 100nm x 20nm) de permalloy dispostas em uma geometria retangular com a razão entre os parâmetros de redes na √ √ √ horizontal (a) e vertical (b) iguais a 2, 3 e 4. O Anti-GSA, trata-se de furos alongados (300nm x 150nm x 30nm) distribuidos em um filme contínuo de níquel, com geometria similar a uma rede GSA com a/b = 1. Ambos sistemas foram estudados através de simulações micromagnéticas e pelas técnicas experimentais de microscopia eletrônica de varredura (MEV), magnetometria de amostra vibrante (VSM) e ressonância ferromagnética (FMR), medidas de magnetorresistência na rede Anti-GSA e microscopia de força magnética (MFM) na rede GSA. Os resultados mostraram que esses sistemas são candidatos promissores para o desenvolvimento de filtros de microondas magnéticos sintonizáveis, além da possibilidade de utilização em outros dispositivos magnéticos. Por fim, o dispositivo híbrido, que é constituído de um sensor magnético do tipo válvula de spin (SV) ou junção túnel magnética (MTJ), um concentrador de fluxo magnético (MFC) e um atuador no plano MEMS comb drive. A elaboração e otimização do processo de fabricação teve como objetivo suprimir o ruído 1/f e tornar o dispositivo capaz de detectar campo magnético a baixas frequências. / In this thesis three systems were manufactured and characterized: the artificial spin ice (ASI), Anti-spin ice (anti-ASI) and a type of hybrid device. The first, ASI consists of a distribution of ferromagnetic nanoislands (300nm x 100nm x 20nm) made of permalloy disposed in a rectangular geometry with ratio between horizontal (a) and vertical (b) √ √ √ lattice parameters equal to 2, 3 and 4. The Anti-spin ice, are elongated holes (300nm x 150nm x 30nm) distributed in a continuous Nickel film, with similar geometry of a rectangular spin ice lattice (ASI) with a/b = 1. Both systems were studied by micromagnetic simulations and experimental scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), ferromagnetic resonance (FMR), magnetoresistance measurements were also made on the Anti-ASI network and magnetic force microscopy (MFM) were made on the ASI network. The results showed that these systems are promising candidates for the development of tunable magnetic microwave filters and possible utilization in other magnetic devices. Finally, the hybrid device, which consists of a spin valve (SV) type magnetic sensor or magnetic tunnel junction (MTJ), a magnetic flux concentrator and an electrostatic MEMS comb-drive actuators. The design and optimization of the manufacturing process, had the main purpose of suppressing the 1/f noise and makinge the device able to detect magnetic field at low frequencies.

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