Abstract : Micromagnetism is the study of the magnetization wich is spontaneously created in ferromagnetic materials. This magnetization, whose norm is constant, is submitted to a free energy. We study the admissible limiting configurations of the magnetization in a few asymptotic regimes. The first result presented in this thesis is about the geometric structure of walls of limiting configurations for a two-dimensional micromagnetic model. The similarity between the micromagnetic problem and scalar conservation laws allows us to obtain, using the same method, a result on the structure of shock waves of some solutions of a scalar conservation law in one space dimension. Finally, we give a kinetic formulation of the mathematical problem associated to a three-dimensional micromagnetic model and we end by a regularizing result for kinetic averaging of the solutions of a liear kinetic equation.