Anisotropic flux pinning energy in FeSexTe1-x single crystals

• FeSexTe1 – x (x = 0.3, 0.4, 0.5, 0.6, 0.7) single crystals were prepared by the chemical reaction. The temperature dependence of the in-plane resistance R(T) of single crystals FeSexTe1 – x were measured.
• Flux pinning energy was studied by Arrhenius relation and the modified thermally activated flux flow (TAFF) model. This result suggests that there is a crossover from single vortex pinning to collective creep pinning region with magnetic field increasing.
• The anisotropy parameter of FeSe0.4Te0.6 was calculated by the means of using the ratio of Hc2 for the two major directions (H//c and H⊥c) and scaling by the equation Hc2GL(θ)=Hc2c/(cos2(θ)+γ−2sin2(θ)).

FeSexTe1 – x (x = 0.3, 0.4, 0.5, 0.6, 0.7) single crystals have been prepared by the chemical reaction of the elements. The field dependence of flux pinning energy shows a power law behavior, U∝H−α, where α displays a crossover at H ∼ 2 T from small value at low field to large value at high field for both magnetic fields perpendicular and parallel to c-axis. At same field, the flux pinning energy for H//ab-plane is higher than that for H//c-axis, showing an anisotropic behavior. The crossover maybe correspond to the flux pinning from single vortex pinning to collective pinning with magnetic field increasing. Based on the anisotropic G-L theory, the angular dependence of in-plane resistivity ρ   in different magnetic fields at fixed temperature can be scaled by the equation, Hc2GL(θ)=Hc2c/(cos2(θ)+γ−2sin2(θ)). The weak temperature dependence of anisotropic parameter γ near Tc was given for FeSe0.5Te0.5 and FeSe0.4Te0.6 crystals, respectively.