Magnetic properties of (FeIn$_2$S$_4$)$_{1-x}$(In$_2$S$_3$)$_x$ alloy single crystals

(FeIn$_2$S$_4$)$_{1-x}$(In$_2$S$_3$)$_x$ alloy single crystals are grown by oriented crystallization in the entire range of component concentrations. For the single crystals, studies of the magnetic properties are carried out in the temperature range 4–300 K and the magnetic-field range 0–14 T. It is established that almost all of the alloys are paramagnetic materials at temperatures down to the lowest achievable temperatures ($\sim$ 4 K). It is shown that the ground magnetic phase state of the alloys is the spin-glass state with the freezing temperature steadily increasing with increasing Fe$^{2+}$ cation content. The most probable causes and mechanism of formation of the magnetic state of the (FeIn$_2$S$_4$)$_{1-x}$(In$_2$S$_3$)$_x$ crystals are discussed.