ULTRASOUND STUDIES OF THE DYNAMICS OF MAGNETICALLY ORDERED CRYSTALS

The current state of ultrasound research on dynamical critical phenome na in magnetically ordered crystals is reviewed. Using the relevant th eoretical concepts, a conclusion is made that the dynamic scaling conc ept and the theory of interacting modes can be used to describe the ex perimental data on ferro-, ferri, and antiferromagnetic materials in b oth the hydrodynamic and critical regions. The influence of the magnet ic field on the dynamics of critical magnetization and spin energy den sity fluctuations is discussed.