Reminder: Magnetic structures description and determination by neutron diffraction

Abstract

The most widespread use of neutron diffraction is of course the determination of magnetic structures, that is the determination of the directions in which moments point in a magnetically ordered material. To describe magnetic structures, it is intuitive and convenient to relate them to the underlying crystal structures, and therefore to use unit cells. But such a simplification misses the elegance of what magnetic structures really are and even makes their description more complex, or impossible in some cases. A more general formalism is required, the formalism of propagation vectors. This lecture is a reminder on what this formalism is, how it can describe the more general structures and how it enters fundamental equations at the basis of magnetic structure determinations by neutron diffraction.