Selfpolarization

Self-polarization is the polarization of a material that exists in the absence of an external electric field. It is closely related to spontaneous polarization, a property of certain non-centrosymmetric crystals and materials with intrinsic electronic or structural asymmetries. In ferroelectric materials, spontaneous polarization can form a macroscopic dipole moment per unit volume that is reversible by applied electric fields.

In ferroelectrics, below the Curie temperature, domains align to produce a measurable polarization. When an external field is removed, part of this polarization may remain, a remanent polarization that reflects the material’s self-polarization in practical terms. The exact extent of self-polarization depends on defects, grain orientation, strain, and boundary conditions, and can be modified by depolarization fields, especially in thin films or near interfaces.

Self-polarization can also arise without deliberate poling through mechanisms that bias domain orientation, such as epitaxial strain, compositional gradients, or interfacial electric fields, leading to self-poling. It is distinct from induced polarization, which only exists under an external field and typically vanishes when the field is removed.

Measurement of self-polarization commonly uses polarization–electric field (P–E) hysteresis loops, pyroelectric current measurements, or local probe techniques that detect remanent dipoles. The concept is described in ferroelectric and dielectric theory with frameworks such as Landau–Devonshire theory, where polarization is treated as an order parameter.

Applications of self-polarized materials include nonvolatile memory, sensors, actuators, and energy harvesting devices. Practical use requires control over stability, fatigue, leakage, and the influence of interfaces and defects.