Solvothermal synthesis and magnetic properties of pyrite Co_1-xFe_xS₂ with various morphologies

Ternary pyrite sulfide Co_1-xFe_xS₂ (0 ≤ x ≤ 1) with various morphologies were synthesized at low temperature via solvothermal process with ethanol as the solvent. Cobalt and iron nitrates were used as starting chemicals, and thiourea as a source of sulfur. Microstructures and magnetic properties were investigated by X-ray diffraction, scanning electron microscope and SQUID magnetization measurements. With the same synthetic condition, the morphology is strongly dependent on Fe doping level x. The grain shape varies from nanoscaled sphericity to round nanorods and finally to rectangle rods with increasing x. Magnetic measurement shows a clear ferromagnetic-paramagnetic transition for the samples with x ≤ 0.5. Broad magnetic phase transition and unsaturated magnetization under high external field are observed, which is due to small grain size. CoS₂ exhibits an effective paramagnetic moment of 1.7 μ_B per Co²⁺, indicative of spin-only electronic structure.