Excitation spectrum and magnetic dynamics of antiferromagnetic nanoparticles in Mössbauer spectroscopy

A continuous model of relaxation in the two-sublattice approximation based on the solution of the equation of motion for the sublattice magnetizations during a continuous relaxation process has been proposed and applied to the description of magnetic dynamics of the ensemble of antiferromagnetic nanoparticles. A non-trivial form of the excitation spectrum of such particles allows a qualitative description of the characteristic shapes of the gamma-resonance spectra depending on temperature, as well as a difference in the spectrum shapes in the regimes of slow and fast magnetic relaxation observed in numerous experiments. The proposed model can be effectively used for quantitative analysis of the experimental spectra of this kind.