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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. [ABSTRACT FROM AUTHOR]

X-ray reciprocal space mapping was used for quantitative investigation of porous layers in indium phosphide. A new theoretical model in the frame of the statistical dynamical theory for cylindrical pores was developed and applied for numerical data evaluation. The analysis of reciprocal space maps provided comprehensive information on a wide range of the porous layer parameters, for example, layer thickness and porosity, orientation, and correlation length of segmented pore structures. The results are in a good agreement with scanning electron microscopy data. [ABSTRACT FROM AUTHOR]

Superparamagnetic particles of Fe3O4 in ferrofluid were injected transcranially in the ventricle of the rat brain. At three months after the injection the rat was sacrificed and the brain was investigated by Mössbauer spectroscopy and histological Perls Prussian blue method. Histological examination demonstrated increased concentration of blue areas in parenchyma and on the dura mater of the brain of experimental rat in comparison with the brain of control rat, indicating appearance in the brain of some undegradable compound of iron. Mössbauer spectra showed the presence in the ferrofluid of both Fe3O4 nanoparticles and an additional chemical compound which contains ferric iron in the high-spin state. Comparison of the Mössbauer spectra of the ferrofluid, of the brain before injection and of the brain three months after injection shows that the Fe3O4 nanoparticles were removed from the brain in three months. At the same time this additional chemical compound does not decompose and remains in the brain intact. [ABSTRACT FROM AUTHOR]

The potential of Mössbauer spectroscopy to study the biodegradation process of magnetic nanoparticles in vivo was demonstrated. Magnetic nanoparticles in form of ferrofluid were administrated to mice. The Mössbauer study of the mice liver samples has shown that in addition to the sextet of lines related to the injected nanoparticles there appears an intense doublet of lines in the spectra with increasing times after the particles administration. Further analysis showed that the doublet consists of two components related to the formation of iron-containing proteins and superparamagnetic behavior of the injected nanoparticles. Using combined analysis of three Mössbauer spectra taken at different external conditions and magnetization curves measured for each sample these components were separated and the evolution with time of each component was characterized. [ABSTRACT FROM AUTHOR]