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

Abstract

We investigate the scaling behavior between Hall resistivity (pxy) and longitudinal resistivity (pxx) in the mixed state and the vortex phase diagram for FeSe0.7Te0.3 (FST) thin films. The pxy and the pxx are simultaneously measured as functions of temperature and magnetic field, and pxy(H, T ) is expressed using the power law relation pxy(H, T) = Apx beta x(H, T ). Interestingly, FST thin films show a two-slope behavior in the power law relation with different exponent values of beta 1 and beta 2. For the temperature sweep (T sweep) at a fixed magnetic field, beta 1 (=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 beta 2 value are relatively small for both cases. Two beta 1 and beta 2 values result in two vortex liquid regimes, which could be ascribed to different pinning strengths within the beta 1 and beta 2 regions. In addition, the tangent of the Hall angle (tant9H) 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 beta 1 and beta 2 regimes. These results suggest that various beta values are possible in FST thin films and are closely related to the flux pinning characteristics.