Proton NMR study of the structural phase transitions in perovskite layer compounds: (CnH2n+1NH3)2CdCl4 and (NH3–(CH2)n–NH3) CdCl4

The temperature dependences of the second moments M2 of the proton magnetic resonance absorption spectra and of the proton spin–lattice relaxation times T1 of perovskite layer compounds (CnH2n+1NH3)2CdCl4 with n=1–3 and (NH3– (CH2)n–NH3) CdCl4 with n=2−5 have been studied together with the frequency dispersion of T1. The structural phase transitions in these compounds were found to be connected with a change in the state of motion of the alkyl or alkylene groups, i.e., by an interplay of transitions between different N–H−−−Cl hydrogen bonding schemes and the excitation of hindered rotations of the hydrocarbon chains.