On the relative contributions of precessional and longitudinal oscillations to the dynamics of magnets

Experimental studies of the high-frequency and acoustic properties of weak ferromagnets are reviewed and a theory that includes all possible mechanisms of the formation of magnet dynamics is presented. The dynamic properties of a magnet are shown to be generally determined by the precessional and longitudinal motions of magnetization and by their interaction with the elastic, paramagnetic, and dipole subsystems. It was found that the precessional and longitudinal contributions always coexist and are additive and that their relative magnitudes depend on both external factors and the relationship (which is characteristic of each specific magnet) between the temperatures of the spontaneous reorientation and ordering of the corresponding spin subsystem. Special attention is paid to the investigation of magnets near the reorientation phase transitions, where the effects due to changes in this relationship, as well as those caused by the interaction of various vibrational subsystems, are most pronounced. (reviews of topical problems)