Patent US 3,936,146

An element in which only a single domain-wall can move sidewise, having a crystal plate of an irregular ferroelectric which is cut in the Z-plane at opposite surfaces and is then cut or cleaved in the <110> direction at its periphery and transparent electrodes for the polarization reversal provided at the central portions of the opposite Z-planes. The element includes at least a domain configuration such that two nucleus regions of opposite polarities are disposed on opposite sides of the region, i.e., a domain having a stationary polarity, where the electrodes are provided.