Lock-in and commensurate transitions of (N(CH₃)₄)₂ZnCl₄ crystals studied by means of real time x-ray synchrotron topography

Abstract

Sequences of I Incommensurate-II Commensurate-Ill Commensurate transitions in TMA₂ZnCL₄, were observed in real time by synchrotron X-ray topography. For I-II transition, the coexistence of commensurate and incommensurate phases causes, on a small temperature range near the lock-in transition, the formation of macroscopic domains bounded by defects which can be identified as deperiodisation lines. These lines have their emergence points on directions which can be indexed in the superspace.