Estimation of spontaneous antipolarization of ADP based on magnitude of fourth‐order electrooptic effect

Abstract

Key words fourth-order electrooptic effect, quadratic electrooptic effect, NH 4 H 2 PO 4 , spontaneous antipolarization. PACS 78.20. Jq, 77.84.Fa Applying the relationship between the spontaneous birefringence of ADP appearing in the low-temperature antiferroelectric phase with the spontaneous antipolarization, and taking into consideration the known experimental values for the quadratic and fourth-order electrooptic effects, an estimate is made of the lower limit of the spontaneous antipolarization. The estimation, which employs the fourth-order electrooptic effect, gives the antipolarization P = 1.2·10-2 Cm -2, a value comparable in magnitude to the spontaneous polarization observed in ferroelectrics belonging to the KDP family of crystals.