Ferroics: Magnetic-Compass Lattice and Optical Phonon Dispersions of Dipolar Crystals
Takeshi Nishimatsu, U Waghmare, Yoshiyuki Kawazoe, Benjamin P. Burton, Kazutaka Nagao, N. Saito
We report a simple safe and attractive pedagogic demonstration with magnetic compasses that facilitates an intuitive understanding of the concept that ferromagnetism and ferroelectricity do not result from dipole-dipole interactions alone. Phonon dispersion relations were calculated for a 3-dimensional simple-cubic dipole crystal and a 2-dimensional square-lattice dipole crystal. The latter calculation corresponds to the compass demonstration that confirm the antiferro ground state structure. A sum rule for the three optical phonon frequencies is discussed. A mathematical non-analyticity in the longitudinal optical phonon are also illustrated.
, Waghmare, U.
, Kawazoe, Y.
, Burton, B.
, Nagao, K.
and Saito, N.
Ferroics: Magnetic-Compass Lattice and Optical Phonon Dispersions of Dipolar Crystals, American Journal of Physics
(Accessed September 26, 2023)