Magnetic walls in nematic liquid crystals

• Autor(a) principal: Simões,M.
• Data de Publicação: 2002
• Outros Autores: Palangana,A.J.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Brazilian Journal of Physics
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97332002000300004

In recent published papers it has been shown that the theory about the formation of magnetic walls in the neighborhoods of the Fréedericksz threshold is in profound disagreement with experiments. This finding leads to the development of a new theory for the onset of these structures in this region of magnetic fields. In this paper we present a review of these developments. The previous theory describing these unstable structures claims that the mode with the fastest initial growth will determine the observed properties of these patterns. But, just above the Fréedericksz threshold, there is a region where this leading mode vanishes and, therefore, a homogeneous bending of the director could be detected. This prediction was not confirmed by the experiment, and walls with very well defined wavelength were found. To explain these experimental facts it has been shown that the fastest growing mode can not be defined around the Fréedericksz threshold and, therefore, a new way to compute the observed periodicity must be formulated. The observed wall results from a sum of a continuum and non-sharp distribution of modes in which the null mode is at the center. This work is written in such away that the main conceptual developments can be easily generalized to systems presenting similar behavior.