Technical properties of magnetic materials

This dossier is the second part of the general presentation of concepts concerning magnetism and the magnetic properties of materials, which is the subject of the article "Physics of magnetic materials" [D 2 080] .

It is dedicated to magnetic properties studied on the intermediate scale of magnetic domains and on the macroscopic scale characteristic of applications.

The first part introduces the essential concepts of Weiss magnetic domain decomposition and Bloch wall decomposition in ferromagnetic materials.

The second part is devoted to the study of mechanisms associated with magnetization variation (coherent rotation and wall movements), initially studied in the context of ideal materials. Some attention is devoted to the influence of dipolar interactions, presented at the scale of the sample (shape effect) or the particle (composite materials). The properties of the real magnetization curve and the hysteresis cycle are then presented, along with the associated quantities. Finally, we devote considerable attention to the properties of dynamic magnetization in the frequency range characteristic of electrotechnical applications. These properties are first presented within the classical framework, before being reinterpreted within the more realistic framework of magnetization mechanisms based on Bloch wall displacement.