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Advances in Condensed Matter Physics
Volume 2017 (2017), Article ID 6209206, 15 pages
https://doi.org/10.1155/2017/6209206
Research Article

Excitation Spectrum of the Néel Ensemble of Antiferromagnetic Nanoparticles as Revealed in Mössbauer Spectroscopy

Institute of Physics and Technology, Russian Academy of Sciences, Nakhimovskii pr. 36-1, Moscow 117218, Russia

Correspondence should be addressed to Mikhail A. Chuev; ur.naitf@veuhc

Received 13 November 2016; Accepted 8 March 2017; Published 11 June 2017

Academic Editor: Jan A. Jung

Copyright © 2017 Mikhail A. Chuev. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The excitation spectrum of the Néel ensemble of antiferromagnetic nanoparticles with uncompensated magnetic moment is deduced in the two-sublattice approximation following the exact solution of equations of motion for magnetizations of sublattices. This excitation spectrum represents four excitation branches corresponding to the normal modes of self-consistent regular precession of magnetizations of sublattices and the continuous spectrum of nutations of magnetizations accompanying these normal modes. Nontrivial shape of the excitation spectrum as a function of the value of uncompensated magnetic moment corresponds completely to the quantum-mechanical calculations earlier performed. This approach allows one to describe also Mössbauer absorption spectra of slowly relaxing antiferromagnetic and ferrimagnetic nanoparticles and, in particular, to give a phenomenological interpretation of macroscopic quantum effects observed earlier in experimental absorption spectra and described within the quantum-mechanical representation.