Relaxation Process in Ferromagnetism

This paper surveys current theoretical work on spin-spin and spin-lattice relaxation in ferromagnetic substances with reference to ferromagnetic resonance. It is shown that it is possible to give a reasonable explanation of the principal features of the experimental results. The calculations, carried out for nickel in particular, make use of a macroscopic spin-lattice interaction determined by the observed magnetostriction and a pseudo-dipolar spin-spin interaction determined by the observed anisotropy. It is not sufficient to use magnetic dipole coupling alone for either of the two relaxation processes. The zero-point fluctuations in the pseudo-dipolar field play a central role in the development of the theory.