HYSTERESIS IN ELECTRIC-DIPOLE MONOLAYERS

The possibility of hysteretic behaviours in plane monolayers of electric dipoles is investigated. The basic tool for this study is a model where the electric dipoles can rotate around the nodes of a plane rhombic grid and the electric interactions among dipoles are properly simplified (Union Jack approximation). In the ideal case of an infinitely extending monolayer, the model yields analytical solutions both for the spatially periodical equilibrium orientations of dipoles and for their stability under the influence of an external electric field. On this basis, a set of hysteresis cycles dealing with different physical situations is obtained and discussed. Then, the much more realistic and complex case of finite-size dipole- monolayers is considered and the hysteresis cycles are obtained by computer calculations. The degree of similarity of these numerical results with the analytical ones of the corresponding infinitely extending monolayers puts into evidence the prediction capabilities of such simple model.