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

Abstract

We investigate the scaling behavior between Hall resistivity (${\ensuremath{\rho}}_{xy}$) and longitudinal resistivity (${\ensuremath{\rho}}_{xx}$) in the mixed state and the vortex phase diagram for ${\mathrm{FeSe}}_{0.7}{\mathrm{Te}}_{0.3}$ (FST) thin films. The ${\ensuremath{\rho}}_{xy}$ and the ${\ensuremath{\rho}}_{xx}$ are simultaneously measured as functions of temperature and magnetic field, and ${\ensuremath{\rho}}_{xy}(H,T)$ is expressed using the power law relation ${\ensuremath{\rho}}_{xy}(H,T)=A{\ensuremath{\rho}}_{xx}^{\ensuremath{\beta}}(H,T)$. Interestingly, FST thin films show a two-slope behavior in the power law relation with different exponent values of ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$. For the temperature sweep ($T$ sweep) at a fixed magnetic field, ${\ensuremath{\beta}}_{1} (=2.0\ifmmode\pm\else\textpm\fi{}0.16)$ 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 ${\ensuremath{\beta}}_{2}$ value are relatively small for both cases. Two ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$ values result in two vortex liquid regimes, which could be ascribed to different pinning strengths within the ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$ regions. In addition, the tangent of the Hall angle $(\mathrm{tan}{\ensuremath{\theta}}_{\mathrm{H}})$ 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 ${\ensuremath{\beta}}_{1}$ and ${\ensuremath{\beta}}_{2}$ regimes. These results suggest that various \ensuremath{\beta} values are possible in FST thin films and are closely related to the flux pinning characteristics.