Prymak T. Exchange magnetic polaritons in many-sublattice magnets

The features of the propagation of eigen-electromagnetic waves and conditions of volume and surface magnetic polaritons formation in many-sublattice magnets are investigated in thesis on an example of well investigated AFM - (-Fe2O3 (hematite). Performed for (-Fe2O3 estimations allow to hope for experimental detection of electroactive spin oscillations by optical methods. The scattering of surface magnetic polaritons in hematite due to the order parameter spatial fluctuations near the spin-reorientational phase transition is investigated. It is found that in characteristic areas of a spectrum the scattering of surface magnetic polaritons has a resonance character. This fact makes the scattering of surface magnetic polaritons due to dielectric susceptibility fluctuations promising for experimental observation. The effect of two-dimensional insulator-metal transition in La2CuO4 on the propagation of photon-magnon modes is investigated. Characteristic polariton structures in calculated transmission spect ra show that magnetic polaritons can be used as a tool for studying of materials with great values of dielectric susceptibility. The frequency-field diagram and components of the tensor of the high-frequency magnetic susceptibility are received for AFM structures realized in La2CuO4+y in a longitudinal magnetic field. The coefficient of the electromagnetic waves propagation through a sample is calculated, and the changes in the propagation spectrum due to the switch-over of the magnetic phases are analysed. Characteristic changes in a spectrum of electromagnetic waves propagation are shown to allow to restore the phase diagram, to determine AFMR frequencies in various phases and on their basis to restore the constants of the spin Hamiltonian of La2CuO4.