PECULIARITIES OF EXCITON AND EXCITON-MAGNON SCATTERING AND RAMAN-SCATTERING OF LIGHT BY QUASI-2-DIMENSIONAL ANTIFERROMAGNET NH3(CH2)2NH3MNCL4

The low-temperature studies of Raman scattering and light absorption spectra of the quasi-two-dimensional antiferromagnet NH3(CH2)2NH3MnCl4 have been carried out. In both spectra peculiarities which deviate from the framework of assumed before two-sublattice model were found. The peculiarities are related with distortions which result in doubling or the crystal lattice period. The analysis of exciton and exciton-magnon absorption bands polarization properties makes it possible to give concrete expression for the nature of these distortions and to make a conclusion about the absence of the symmetry centre in the Mn2+ magnetic ion position.