Estudo analítico de sistemas de Heisenberg bidimensionais dopados e com acoplamentos anisotrópico e biquadrático

• Ano de defesa: 2011
• Autor(a) principal: Moura, Antônio Ribeiro de
• Orientador(a): Pereira, Afrânio Rodrigues
• Banca de defesa: Silva Neto, Marcelo Barbosa da , Wysin, Gary W.
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Física
• Departamento: Física Teórica e Computacional; Preparação e Caracterização de Materiais; Sensores e Dispositivos.
• País: BR
• Palavras-chave em Português: Magnetismo; Soluções topológicas; Modelo de Heisenberg
• Palavras-chave em Inglês: Magnetism; Topological solutions; Heisenberg model
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA
• Link de acesso: http://locus.ufv.br/handle/123456789/956

In the work development we have studied magnetic models by two different approaches. In the two first models was used the continuum approximation to anti-ferrogmagnetic givem by O(3) non-linear sigma model (NLSM). This model is similar to the Yang-Mills theory and it is well known that it supports topological configurations as solutions, the so-called skyrmions. Initially we have studied how an anisotropic term (similar to magnetic anisotropy) influences in the solutions. We have noted that quantum perturbations are responsible for spin field interactions that do not exist in a semi-classical limit. In another work, we verified that the inclusion of a non-magnetic impurities creates a harmonic potential interaction between the skyrmion and the defect. The topological solution is restrained by defect and that capture is important to many applications in magnetic devices. We also have studied other two models by Schwinger bosonic transformations. In one of them, it has shown a separation between an ordered and disordered phases to biquadratic model due to an anisotropic term. Finally, we have applied the bosonic therory to biquadratic model in a honeycomb hexagonal lattice to T=O and low temperatures.