On the polarization of ferroelectrics

Polarization is an important physical observable for understanding ferroelectricity. In this paper, the polarization of ferroelectric materials is discussed based on the hysteresis loop and Sawyer–Tower circuit. The relationship between polarization and internal electric field or effective field is addressed. The key issue is that higher-order electric moments are necessary for the polarization in ferroelectrics. A plausible definition of polarization for ferroelectric material is proposed. The validity of the current concepts and theories, such as domain theory, thermodynamic theory, and Maxwell’s equations, is analyzed.