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

• Autor(a) principal: Moura, Antônio Ribeiro de
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/956
• topic: Magnetismo; Soluções topológicas; Modelo de Heisenberg; Magnetism; Topological solutions; Heisenberg model; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

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.