Physics of magnetic materials

This dossier is the first part of a general presentation of notions and concepts concerning magnetism and the magnetic properties of materials. A pragmatic presentation of the various useful basic notions enables us to grasp the essential properties at different scales, from the atomic to the macroscopic.

The first part is devoted to a review of magnetostatics and the notion of magnetic polarization and its relationship to the magnetic excitation and induction fields. This is followed by a presentation of the magnetic properties of the atom in the free and bound states, and an introduction to the concepts of spin-orbit coupling and crystal field, fundamental interactions in terms of the properties of use that will determine the two major families of soft and hard materials. The more difficult theoretical aspects (concerning, for example, the itinerant magnetism characteristic of metallic alloys) have been deliberately left aside.

A phenomenological presentation of the main magnetic behaviors characteristic of the microscopic scale, the various energy terms characteristic of the ferromagnetic state and associated behaviors, and magnetoelastic properties are the subject of the final section.

A second dossier [ D 2 081 ] completes this first presentation, presenting magnetic properties on the scale of Weiss magnetic domains and the main concepts and properties of magnetization on the macroscopic scale.