Detection of slow modulation wave diffusion in incommensurate barium sodium niobate by Nb-93 two-dimensional exchange NMR - art. no. 012406

Nb-93 two-dimensional (2D) exchange NMR was used to study ultraslow motions in incommensurate barium sodium niobate (SN) in the temperature range 500- 560 K. These 2D exchange data provide strong evidence for diffusionlike mot ion of the modulation wave in BSN. Such motions in BSN had been previously detected by using a complementary NMR experiment, the Hahn spin-echo decay. However, since the Hahn spin-echo decay technique cannot always distinguis h unambiguously between different motional mechanisms, this 2D experiment p rovides definitive confirmation of modulation wave diffusion and rules out other possible motional mechanisms for the Hahn spin-echo decay in this sys tem.