Magnetic properties of (FeIn$_2$S$_4$)$_{1-x}$(CuIn$_5$S$_8$)$_x$ single-crystal alloys

The magnetic properties of (FeIn$_2$S$_4$)$_{1-x}$(CuIn$_5$S$_8$)$_x$ single-crystal alloys are studied in the temperature range 4–300 K and in the field range 0–14 T. It is established that almost all of the alloys are paramagnetic materials at temperatures down to the lowest temperatures ($\sim$ 5 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 content of Fe$^{2+}$ cations. The most probable causes and mechanism for formation of the magnetic state of (FeIn$_2$S$_4$)$_{1-x}$(CuIn$_5$S$_8$)$_x$ single-crystal alloys are discussed.