Abstract
The NMR chemical shifts, linewidths, spin-lattice relaxation times in the rotating system T(1ρ), and spin-lattice relaxation times in the laboratory system T(1) were evaluated for the perovskite-type N(CH(3))(4)CdBr(3) crystal, aiming to understand the changes in the structural geometry and molecular dynamics from phase I to phase II. From the temperature-dependence of the (1)H, (13)C, (14)N, and (113)Cd NMR chemical shifts, the structural geometry underwent a continuous change, without anomalous changes around (T(C) = 390 K). However, the linewidths in phase I were narrower than those in phase II, indicating that the motional averaging effects were caused by the rapid rotation of the N(CH(3))(4) group. Sudden changes in T(1) and T(1ρ) were observed near T(C), for which the activation energy E(a) in phase I was approximately 12 times larger than that in phase II; the small E(a) values in phase II indicate a large degree of freedom for the methyl group and CdBr(6) octahedra, whereas the large E(a) in phase I was primarily attributed to the overall N(CH(3))(4) and the (113)Cd in the CdBr(6) groups. Consequently, the phase transition mechanisms of N(CH(3))(4)CdBr(3) are related to reorientation of the N(CH(3))(4) group and the arrangement of the CdBr(6) groups.