Abstract
Dielectric permittivity studies in the field-cooled mode show a linear dependence of dielectric stiffness (inverse dielectric permittivity) on dc bias in PbMg1/3Nb2/3O3–PbTiO3 crystals and some other relaxors above a certain threshold bias value. The observed behavior can be described by extrinsic contributions like 90°-domain wall movements and/or rotations of dipole moments (polarization-rotation).