SPECIAL CHARACTERISTICS OF NONLINEAR RESONANCE VIBRATIONS OF SAMPLES IN THE VICINITY OF DIFFUSIONLESS PHASE-TRANSITIONS

It is established that the activation of phase transitions by stresses can impart nonlinearity to resonance vibrations of materials near diffusionless phase-transition temperatures. Such nonlinearity is manifested in the asymmetry of the resonance peaks, a dependence of their shape on the direction in which the frequency is varied in passage of the sample through resonance, and a periodic variation of the vibration amplitude. The conditions for the onset of various vibration regimes are determined. It is noted that nonlinearity is attributable to diffusionless second-order phase transitions in magnets, ferroelectrics, and superconductors.