Radiation Damping in Magnetic Resonance Experiments

TLDR

Magnetic resonance experiments are modeled as coupled circuits—an electrical resonant circuit and a rotating magnetization—where transient phenomena cause damping of the resonance, known as spontaneous radiation damping. The study shows that in some nuclear induction scenarios radiation damping can outweigh conventional spin‑spin and spin‑lattice relaxation, and it can become very large in ferromagnetic materials at microwave frequencies.

Abstract

Magnetic resonance experiments can be described by analogy to a coupled pair of circuits, one of which is the ordinary electrical resonant circuit. The other circuit is formed by the rotating magnetization. For transient phenomena, such as occur, e.g., in the pulse techniques of free nuclear induction, the coupling gives rise to a damping of the magnetic resonance by the electric circuit. Such damping can also be considered as spontaneous radiation damping. It is shown that in certain cases of nuclear induction this radiation damping is more important than the damping from the spin-spin and the spin-lattice relaxation mechanisms usually considered. For ferromagnetic materials at microwave frequencies the radiation damping can become very large.