Relative contribution of the precessional and longitudinal oscillations tothe dynamics of magnets

Experimental studies of the microwave and acoustical properties of weak fer romagnets are reviewed and a theory which includes all possible dynamics fo rmation mechanisms in magnets is presented. It is shown that the dynamic pr operties of a magnet are generally determined by the precessional and longi tudinal magnetization oscillations and by their coupling to elastic, magnet ic and dipole subsystems. It is found that the precessional and longitudina l contributions always coexist and are additive and that their relative mag nitudes depend on both external parameters and on the relevant spin subsyst em's spontaneous reorientation to ordering temperature ratio, a characteris tic quantity for every particular magnet. Special attention is given to the neighbourhood of reorientation phase transitions, where the effects arisin g from the change of the temperature ratio as well as from the coupling of different oscillatory subsystems ale at their strongest.