QUADRUPOLE RELAXATION OF BR-79 NUCLEI IN FERROELECTRIC (CH3)(4)NCDBR3(TMCB)

Investigations of temperature dependence of a nuclear quadrupole spin- lattice relaxation time of Br-79 nuclei in ferroelectric (CH3)(4)NCdBr 3 are presented. It is shown that in paraelectric phase in the vicinit y of phase transition temperature relaxation process is determined by critical fluctuations of electric field gradient. In ferroelectric pha se relaxation is related to three different mechanisms, namely: lattic e vibrations, CH3-group reorientations and TMA cation motions. Accordi ng to the results of measurements it is concluded that the phase trans ition is connected with ordering of TMA cations.