Specific heat study of ferroelectric CsH₂PO₄ and CsD₂PO₄

For ferroelectric CsH₂PO₄ and CsD₂PO₄ the specific heat has been measured using an AC calorimeter. The singularity of the specific heat at the phase transition point is logarithmic. The most characteristic feature of the behaviour is the existence of an anomalous specific heat over the wide temperature region from T_c-60K to T_c+60K. This anomalous specific heat is considered to be due to the one-dimensional fluctuation of the polarisation in these materials. The authors also compare the experimental results with the pseudo-one-dimensional Ising model.