Nontrivial dependence of dielectric stiffness on bias field in relaxors and dipole glasses

Dielectric permittivity studies in the field-cooled mode show a linear dependence of dielectric stiffness (inverse dielectric permittivity) on the dc bias in (1−x)PbMg1∕3Nb2∕3O3−xPbTiO3 crystals. We explain this unusual result in the framework of a theory of transverse, hydrodynamic-type instability of local polarization.