ABSTRACT

Ions with strong spin–orbital coupling emerge either as a result of the impurities in the starting materials or due to the change of the main-ion valencies. In some cases the ions with strong spin–orbital coupling are added purposely, e.g., to increase the threshold of parametric spin-wave excitation. The contribution of the ionic relaxation process to the ferromagnetic-resonance linewidth of ferrites was observed, as it became clear afterwards, in the early 1950s. The fast relaxation falls into the transverse relaxation mechanisms, for which the excitation of ions is accomplished by means of direct transitions between ionic energy levels. This excitation is analogous, in some sense, to the paramagnetic resonance, with the difference that it is performed by the magnons of the main magnetic system, rather than by quanta of an external field. And, finally, along with the relaxation processes involving phonons, analogous processes with the participation of magnons (ion–magnon processes) can take place.