On the thermodynamics of antiferromagnetic nanoparticles by example of Mцssbauer spectroscopy

A quantum-mechanical model has been developed for describing the thermodynamics of an ensemble of ideal antiferromagnetic nanoparticles in the approximation of slowly relaxing macrospins of magnetic sublattices. This model is the foundation for the further development of the general theory for the magnetic dynamics of antiferromagnetic and ferrimagnetic nanoparticles. Moreover, it already allows a qualitative description of the difference between the thermodynamic properties of nanoparticles of different magnetic natures, including quantum effects, which have been observed for almost fifty years in many experimental Mцssbauer absorption spectra of $^{57}$Fe nuclei in antiferromagnetic nanoparticles.