On the growth and properties of FeIn$_{2}$S$_{3.6}$Se$_{0.4}$ single crystals

FeIn$_{2}$S$_{3.6}$Se$_{0.4}$ single crystals are grown by planar crystallization of the melt (the vertical Bridgman method). The composition and crystal structure of the crystals are determined. It is established that the single crystals crystallize with the formation of the cubic spinel structure. From the transmittance spectra in the region of the fundamental absorption edge, the band gap of the single crystals is determined. Thermal expansion of the FeIn$_{2}$S$_{3.6}$Se$_{0.4}$ single crystals is studied by the dilatometric technique in the temperature range from 80 to 550 K, and the coefficients of thermal expansion are determined. From the coefficients of thermal expansion determined, the Debye temperatures and the root-mean-square (rms) dynamic displacements of atoms are calculated. It is shown that, as temperature is elevated, the Debye temperatures decrease and the rms dynamic displacements of atoms increase. Magnetic studies show that the FeIn$_{2}$S$_{3.6}$Se$_{0.4}$ single crystals are paramagnetic materials at temperatures down to 12.4 K.