ELEMENTARY EXCITATIONS IN FERROELECTRIC-A NTIFERROMAGNETIC MATERIAL WITH JAHN-TELLERS IONS

The spectrum of elementary excitations of a uniaxial ferroelectric-ant iferromagnetic material with Jahn-Teller's ions is taken at magnetic f ields H parallel and perpendicular to equilibrium electric polarizatio n P0. It has been shown that the noncommutativity of the electric pola rization- and magnetic moment operators of a Jahn-Teller ion induces h igh-frequency oscillations of the magnetic moment (H perpendicular-to P0), magnetic field splitting of a degenerated optical phonon branch a nd precession of the electric polarization vector (H parallel-to P0). These effects are also possible in a paramagnetic crystal in external electric and magnetic fields.