Evidence of memory effects in a commensurate ferroelectric phase

Dielectric measurements in [N${\left(\mathrm{C}{\mathrm{H}}_3\right)}_4$]${}_2{}^{}{}_{}{}^{}\mathrm{Co}$ ${\mathrm{Cl}}_4$ crystals are reported that show that memory effects in materials exhibiting incommensurate phases are not exclusively limited to these phases but can also appear in commensurate ones. The dielectric susceptibility of the material suffers strong anomalies in the ferroelectric commensurate phase after annealing in this phase for a few hours. The characteristics of this new effect are more complex than those previously reported within incommensurate phases.