Transport properties of iron dichalcogenides FeX2 (X = S, Se and Te)

Iron dichalcogenides FeX2 (X=S, Se and Te) attract interest as semiconducting material containing narrow 3d band. FeS2 crystallizes in a cubic pyrite-type structure, and both FeSe2 and FeTe2 in an orthorhombic marcasite-type one. Electrical resistivity (rho), Hall coefficient (R-H) and thermoelectric power (S) were studied on the synthetic samples of iron dichalcogenides FeX2 (X=S: Se and Te) in the wide temperature range (77 K-600 K). The measurements of rho, R-H, and S were done for the same sample which is made in the proper preparation condition to get the mutually complementary informations with each other. All the prepared compounds are semiconductive at temperatures from 77 K to 600 K. Energy gaps, E-Gh (rho) and E-Gh (R-H), are estimated from the temperature dependence of rho and R-H in the region at high temperatures. The energy gap was found to decrease systematically from FeS2 to FeTe2.