Nutations of magnetizations of sublattices and their role in the formation of Mössbauer spectra of antiferromagnetic nanoparticles

The continuum model of the magnetic dynamics of an ensemble of antiferromagnetic nanoparticles in the two-sublattice approximation has been generalized to the case of the exact solution of the equations of motion for magnetizations of sublattices. The nontrivial excitation spectrum of such particles in the form of four excitation branches corresponding to the normal modes of self-consistent precession of magnetizations of sublattices, as well as the continuous spectrum of nutations of magnetizations accompanying these modes, corresponds completely to quantum-mechanical calculations and makes it possible to give a phenomenological interpretation of macroscopic quantum effects earlier observed in many experimental Mössbauer absorption spectra.