Static dielectric behavior of dipolar glasses

The understanding of the behavior of dipolar glasses has drawn heavily from the theory of conventional spin glasses. Nevertheless, some important aspects of the physics of dipolar glasses are absent in the spin systems. Because dipoles couple to electric rather than magnetic fields, quenched random fields, arising from lattice distortions, are almost always present in dipolar glasses. Also, in mixed families of compounds, like (BP)(1-x)(BPI)(x) studied here, the end members of the series display clear quasi-one-dimensional character. We present here a systematic study of the static dielectric behavior in the paraelectric phase of this family of compounds and compare it to the predictions of several theoretical models. We were able to distinguish between quasi-one-dimensional and isotropic compounds, and to determine the values of parameters characterizing the interactions and the random electric fields; these, in turn, allow a determination of the Almeida-Thouless temperatures for the compounds with a glass phase. This work, together with structural and x-ray studies, leads to a detailed proposal for the phase diagram of this family of compounds.