Effect of the partial substitution of Zn2+ ions in (CH3NH3)2ZnCl4 with Co2+ ions on the structure, phase transition, and molecular motion

Abstract

The effects of the partial replacement of Zn2+ ions with paramagnetic Co2+ ions on the physical properties of (CH3NH3)2Zn1-xCoxCl4 (x = 0, 0.3, 0.5, 0.7, and 1) crystals are discussed. These crystals are grown using the slow evaporation method, and their structures and phase-transition temperatures are measured through X-ray diffraction and differential scanning calorimetry experiments. The structures and phase transition temperatures for cases, where x = 0.3 and 0.5, and x = 0.7 are similar to those for x = 0, and x = 1, respectively. In addition, the spin-lattice relaxation time, T1ρ, in the rotating frame are measured for the 1H and 13C nuclei of the (CH3NH3)+ cations to understand the molecular motions with respect to the Co2+ ion quantity. The molecular motions for 1H and 13C with x = 0.5 are similar to those with x = 0, whereas those with x = 0.7 are similar to the x = 1 case. The molecular motions of (CH3NH3)+ ions bounded to the Co2+ layer through N–H⋯Cl bonds differ from those bounded to the Zn2+ ions.