Structural and Transport Studies of Under-Doped FeTe 1 − x Se x (x =0.0, 0.01, 0.03, 0.05) Single Crystals

We report the synthesis of under-doped non-superconducting parent compound of iron chalcogenide, i.e, FeTe 1−xSe x (x =0.0, 0.01, 0.03, 0.05) single crystals by flux-free method. These FeTe 1−xSe x (x =0.0, 0.01, 0.03, 0.05) single crystals are crystallized in the tetragonal structure with space group P4/nmm at room temperature. Detailed scanning electron microscopy (SEM) results showed that the crystals are formed in slab-like morphology structure. Powder X-ray diffraction (XRD) results show that (0 0 l) peaks are shifted towards higher angel with increasing Se concentration. Coupled magnetic and structural phase transition temperature, being seen as a step in resistivity, decreases from around 67K for x =0.0 to 55K for x =0.05 crystal. Further, the step in resistivity is seen to be hysteric (ΔT) in nature, i.e., different step temperatures in cooling and warming cycles. Interestingly, the hysteric (ΔT) becomes narrower from around 5.8 K for x =0.0 to 0.95 K for x = 0.05 crystal.