Direct Current Measurement of Hall Effect in the Mixed State for the Iron-chalcogenide Superconductors

In order to investigate how the composition and the pinning affect the behavior of the Hall effect in the mixed state, we measure the Hall resistivity for iron-chalcogenide superconductor FeSe_1−xTe_x films near the superconducting transition temperature. We observe a sign change of the Hall resistivity in FeSe_0.5Te_0.5 (x = 0.5) films, but FeSe_0.8Te_0.2 (x = 0.2) films do not show the sign reversal. Increasing applying current density, the sign change of the Hall resistivity in the film with x = 0.5 disappeared. We evaluated the strength of the pinning in samples from an activation energy and a scaling law, and found that the film with x = 0.5 has the stronger pinning than that of the film with x = 0.2. All of those results suggest that the pinning has related to the Hall resistivity anomaly in Fe chalcogenides.