Ferroelectric Properties of X-ray Damaged Rochelle Salt

Radiation damage effects by X-ray in rochelle salt are studied experimentally and theoretically. Double hysteresis loop is explained as a superposition of two biased single loops. Each biased single loop corresponds to each of the two oppositely polarized domains, of which the crystal is composed. Single domain crystals show biased single loops when damaged, and the internal bias thus induced can be compensated by an external dc biasing field. But the Curie point of the damaged crystals compensated by this suitable external field is lower than that of the virgin by Δ T , which depends upon the X-ray dosage. In this respect the effect of damage differs from that of the stress. It is assumed that the irradiation gives rise to polar anisotropy centers which produce effective bias fields in undamaged ferroelectric regions. Irradiation time dependences of the spontaneous polarization, the coercive field and the internal bias are studied. A phenomenological theory is developed to explain the various phenomena. The polarization within the polar anisotropy center is estimated to be the order of 100 esu near the shifted Curie point.