Estudo do fenômeno de exchange bias em bicamadas NiFe/IrMn e tricamadas NiFe/IrMn/Co

• Ano de defesa: 2013
• Autor(a) principal: Sousa, Marcos Antonio de
• Orientador(a): Pelegrini, Fernando
• Banca de defesa: Pelegrini, Fernando, Geshev, Julian Penkov, Feitosa, Carlos Chesman de Araújo, Bakuzis, Andris Figueiroa, Castro, Marcos Antônio de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Goiás
• Programa de Pós-Graduação: Programa de Pós-graduação em Física (IF)
• Departamento: Instituto de Física - IF (RG)
• País: Brasil
• Palavras-chave em Português: Ressonância de spin (elétron); Ressonância ferromagnética; Anisotropia magnética; Magnetização
• Palavras-chave em Inglês: Electron spin resonance
• Área do conhecimento CNPq: FISICA::FISICA DA MATERIA CONDENSADA
• Link de acesso: http://repositorio.bc.ufg.br/tede/handle/tede/3619

This work reports the study of the phenomenon of exchange bias in NiFe/IrMn bilayers and NiFe/IrMn/Co trilayers. In the NiFe/IrMn bilayers, ferromagnetic resonance experiments at X and Q bands microwave frequencies reveal that spin wave and NiFe resonance modes are excited by the oscillating microwave field. Angular variations of the absorption fields in the plane of the films for both resonance modes shows the effect of the unidirectional anisotropy field, whose intensity is twice larger for the spin wave mode, due to an additional contribution of an unidirectional surface anisotropy. The experiments also indicate the presence of a uniaxial anisotropy of the NiFe layer, apparently dependent on the applied magnetic field. The magnetic parameters of both resonance modes were deduced considering a generalized phenomenological model which also includes the contribution of a rotatable anisotropy. In the NiFe/IrMn/Co trilayers, the angular variations of the resonance field in the plane of the films reveal the effect of the unidirectional anisotropy field for both independent resonance modes of NiFe and Co layers. The ferromagnetic resonance results combined with magnetometry data show that the exchange bias phenomenon at the NiFe/IrMn interface influences the same phenomenon at the IrMn/Co interface, and that this effect must be mediated by a spiral structure of spins across the IrMn antiferromagnetic layer. For both systems studied, the values of the exchange bias field deduced from the ferromagnetic resonance experiments are consistent with the values given by magnetization measurements.