Polarization echoes and long-time storage in piezoelectric powders

Two- and three-pulse polarization echoes are detected in powders of mechanically resonant particles of piezoelectric materials. Under some conditions the decay time of the three-pulse echo can be of order one day or longer. A model for the echo formation and long decay time based upon the torque exerted on an oscillating dipole by an applied rf field is described. © 1976 The American Physical Society.