Spectroscopic Study of Structural Phase Transition and Dynamic Effects in a [(CH3)2NH2][Cd(N3)3] Hybrid Perovskite Framework

We present a combined study of [(CH3)2NH2][Cd(N3)3] hybrid perovskite dense metal-organic framework by IR, Raman, continuous-wave electron paramagnetic resonance (CW EPR), phase-transition-induced current and dielectric measurements. The Raman and IR study has shown that the phase transition observed near 175 K is associated with a pronounced narrowing and intensity increase of bands related to the NH2 group of dimethylammonium (DMA+) cations located in the cavities of the framework. This observation has proved that the phase transition is associated with an ordering of DMA+ cations. The dielectric response of [(CH3)2NH2][Cd(N3)3] single crystal has revealed a weakly expressed anomalous behavior of the dielectric constant at the phase transition point. In the low-temperature phase a pronounced dispersion in the kilohertz frequency range has been observed, which might be assigned to the two-fold reorientation dynamics of the DMA+ cations. The phase-transition-induced current measurements of DMACd(N3)3 sing...