Dielectric properties of the quasi-one-dimensional hydrogen-bonded ferroelectric crystal PbHPO4

Abstract
The static dielectric constant of the hydrogen-bonded ferroelectric PbHPO4 has been measured and the results have been analysed by the quasi-one-dimensional Ising model. The value obtained for the effective dipole moment disagrees with the corresponding value obtained from spontaneous polarisation measurements. The analysis of three-dimensional hydrogen-bonded ferroelectric systems shows that the neglect of tunnelling between the two positions in a hydrogen bond leads to such discrepancies. It is concluded that the tunnelling should be taken into account in PbHPO4 as well as in PbDPO4.