Title: Dipole oriented matter: a novel ferroelectric state Speaker: David Field, IFA Time: Thursday, January 27, 15.15 to 16.00 Place: Fysisk Auditorium Abstract: Seemingly prosaic films of chemicals such as nitrous oxide or propane have been found to harbour very large spontaneous electric fields which can be greater than 10^8 V/m. I will describe how the discovery of this unexpected phenomenon took place and how we attempt to understand the nature of the new class of ferroelectric materials which these observations herald. The molecules so far identified form a diverse group of six species with dipoles lying between 0.08 Debyes and 0.5 Debyes : propane (0.08D), isopentane (0.13D), nitrous oxide (N2O: 0.167D), isoprene (0.25D), toluene (0.385D) and CF3Cl (Freon-13; 0.5D). I will concentrate on an understanding of the structure of the ferroelectric state using the measured temperature dependence of the spontaneous electric field in N2O as a diagnostic, showing that the ferroelectric state is generated through dipole alignment in the form of a single domain. The discovery of this new type of material may have wide ranging applications in device and nano-technology and also influence the electrical nature of dust in the interstellar medium. Jacob Sherson and Aurélien Dantan Coffee, tea and cake will be served at 15.05 Dr. Jacob Friis Sherson Institut for Fysik og Astronomi Aarhus Universitet Ny Munkegade 120 8000 Århus C Tel.:8942 3680