Mixed-state Hall scaling behavior and vortex phase diagram in FeSe0.7Te0.3 thin films

We investigate the scaling behavior between Hall resistivity (ρxy) and longitudinal resistivity (ρxx) in the mixed state and the vortex phase diagram for FeSe0.7Te0.3 (FST) thin films. The ρxy and the ρxx are simultaneously measured as functions of temperature and magnetic field, and ρxy(H,T) is expressed using the power law relation ρxy(H,T)=Aρxxβ(H,T). Interestingly, FST thin films show a two-slope behavior in the power law relation with different exponent values of β1 and β2. For the temperature sweep (T sweep) at a fixed magnetic field, β1 (=2.0±0.16) is insensitive to the magnetic field, whereas for the magnetic field sweep (H sweep) at a fixed temperature, the value significantly increases from 1.93 to 3.82 with an increase in temperature. On the other hand, changes in the β2 value are relatively small for both cases. Two β1 and β2 values result in two vortex liquid regimes, which could be ascribed to different pinning strengths within the β1 and β2 regions. In addition, the tangent of the Hall angle (tanθH) with respect to the magnetic field exhibits a crossover behavior at the critical field H∗, which coincides with the magnetic field corresponding to the boundary of the β1 and β2 regimes. These results suggest that various β values are possible in FST thin films and are closely related to the flux pinning characteristics.