  The distribution of magnetic moments in finite ferromagnetic bodies was first
investigated by Landau and Lifshitz in a famous paper [\textit{Phys. Z. Soviet
Union}, \textbf{8}, 153 (1935)], where they obtained the domain structure of a
ferromagnetic crystal at low temperatures, in the regime of saturated
magnetization. In this article, we investigate the general properties of
ferromagnetic domain walls of uniaxial crystals from the view point of the
Landau free energy. We present the basic ideas at an introductory level, for
non-experts. Extending the formalism to the vicinity of the Curie temperature,
where a general qualitative description by the Landau theory of phase
transitions can be applied, we find that domain walls tend to suppress the
layers, leading to a continuous vanishing of the domain structure with
anomalous critical exponents. In the saturated regime, we discuss the role of
domain walls in mesoscopic systems and ferromagnetic nanojunctions, relating
the observed magnetoresistance with promising applications in the recent area
of spintronics.
