Magnon satellite bands in the optical spectrum of antiferromagnetic Rb2MnCl4

The evolution of optical absorption in a two-dimensional antiferromagnet is investigated in the range of the transition (6)A(1g)-->(4)A(1g), E-4(g)((4)G) observed in manganese ions in an external magnetic field inducing noncollinearity of the magnetic structure. It is revealed that hot and cold satellites of the exciton-magnon bands appear in the optical absorption spectrum and then increase in intensity. The shapes of the magnon satellite bands corresponding to a two-dimensional magnetic structure are calculated. It is demonstrated that magnons at the inner points of the Brillouin zone appreciably contribute to the absorption. The zero-point magnetic oscillations play a decisive role in the absorption associated with the magnon decay at low temperatures. (C) 2003 MAIK "Nauka/Interperiodica".