Structural Phase Transition of Perovskite-Type N(CH3)4CdBr3 Studied by MAS NMR and Static NMR

Аннотация

The structural geometry change in the perovskite-type N(CH₃)₄CdBr₃ single crystal near the phase transition temperature of T_C = 390 K was investigated using magic angle spinning nuclear magnetic resonance techniques. For ¹H and ¹³C nuclei, the temperature dependences of their chemical shift, spectral intensity, and spin–lattice relaxation time (T_1ρ) in the rotating frame were obtained and analyzed. While the chemical shift and T_1ρ of ¹H showed change near T_C, those of ¹³C did not. In addition, the ¹¹³Cd spin–lattice relaxation time T₁ in the laboratory frame near T_C show no evidence of anomalous change near the phase transition temperature, which coincides with the measured changes in the ¹H T_1ρ. The driving force for this phase transition was connected to the ¹H in the CH₃ groups.