Features of the magnetic structure of Y$_{3}$Fe$_{5}$O$_{12}$ polycrystals synthesized by radiation thermal sintering

Samples of polycrystalline yttrium-iron garnet synthesized using radiation-thermal sintering and ceramic processing have been studied by the Mössbauer spectroscopy method. The best decomposition of the Mössbauer spectroscopy spectra of the research objects, which is a simulation of the experimental spectrum with five sextets, has been selected. An additional fifth sextet is caused by Fe$^{3+}$ ions, which are surrounded by oxygen vacancies leading to distortion of Fe-tetrahedra, which is reflected in an increase in the quadrupole splitting of Fe$^{3+}$. An increase in the density of $s$-electrons on Fe ions in distorted tetrahedra has been found, resulting in a decrease in the isomeric chemical shift $\delta$ of Fe ions to a value close to the $\delta$ value for Fe$^{4+}$ ions. It has been shown that the optimal crystal structure is realized in Y$_{3}$Fe$_{5}$O$_{12}$ polycrystals when they are sintered for 40–60 min in the temperature range of 1350–1400$^\circ$C by the radiation-thermal sintering method.