Kurnosov V. Spectroscopy of multisublattice antiferromagnets with a strong interaction of magnetic, electronic and lattice excitations

The thesis is devoted to establishing the dependence between the structural features of multisublattice antiferromagnets and the formation of their magnetic, electronic and vibrational states. The appearance of phonon peaks in the Raman spectra of CsFeCl3•2H2O from the boundary of the Brillouin zone at antiferromagnetic ordering is revealed and its mechanism is explained. The two-magnon Raman band in the antiferromagnetic CsMnCl3•2H2O is revealed, and it is shown that the reason for its appearance in the spectrum is the zigzag structure of chains formed by the magnetic ions. It is shown that the unusual form of a two-magnon Raman band in quasi-two-dimensional nickelates is due to the influence of charge stripes on the spin-dependent polarizability. It has been found that in quasi-one-dimensional geometrically frustrated antiferromagnets with triangular structural clusters the practically non-dispersive flat-band modes can be formed. In many examples of multisublattice predominantly antiferromagnetic compounds the role of interactions between degrees of freedom of various origins on the formation of the excitations spectra is shown.