DC transport properties of Fe(Se,Te) crystals: Effects of Se substitution into Te site

FeTe is an antiferromagnetic semimetal and superconductivity shows up when Te is substituted with Se, but effects of Se substitution are still unclear. To elucidate this issue, we study the behavior of Hall resistance in detail using single crystalline FeSe$_x$Te$_{1-x}$ with $x = 0$ to 0.4. Single crystals are grown by Bridgman method, and Hall resistance is analyzed within the standard 2-carrier model. We find that the electron density $n_e$ is larger than the hole density $n_h$ for $x \leq 0.3$ samples, but $n_h$ becomes greater than $n_e$ for $x = 0.4$ crystal. We also find that electron mobility enhances especially at low temperatures with Se substitution.