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

Abstract

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 (C_nH_2n+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.