Synthesis of FeS Nanoparticles with Various Superstructures by a Simple Thermal Decomposition Route and Their Magnetic Properties.

Pyrrhotite nanoparticles with 5C and 3C superstructures were synthesized via a simple one-step thermal decomposition method in which hexadecylamine was used as a solvent at various reaction temperatures (T). Structural analysis showed that at T = 360 °C, almost uniform in size and shape FeS nanoparticles with 3C superstructure are formed, and an increase in the reaction temperature leads to the formation of FeS nanoparticles (5C superstructure), herewith a significant increase in the size of nanoparticles is observed. High-temperature magnetic measurements in 5 repeated heating-cooling cycles revealed that after the first heating branch in the FeS samples, the λ-Peak transition disappears, and the magnetization has a Weiss-type behavior characteristic of the FeS sample. The change in the behavior of magnetization can be explained by the redistribution of iron vacancies, which changes the initial phase composition of nanoparticles.