Transport properties of Li_x(NH₃)_yFe₂(Te_zSe_1−z)₂ single crystals in the mixed state

We study the electric transport properties of Li_x(NH₃)_yFe₂(Te_zSe${}_{1-z}$)₂ single crystals with $z=0$ and 0.6 in the mixed state. Thermally-activated flux-flow, vortex glass and flux-flow Hall effect (FFHE) behaviors are observed. Experimental results show that there are rich vortex phases existing in these systems and the vortex liquid states occupy broad regions of phase diagrams. Further analysis suggests that thermal fluctuation plays an important role in the vortex phase diagrams of Li_x(NH₃)_yFe₂(Te_zSe${}_{1-z}$)₂. Moreover, for Li_x(NH₃)_yFe₂Se₂, there is no sign reversal of FFHE in the mixed state and a scaling behavior $|{\rho }_{xy}{\left({\mu }_{0}H\right)|=A{\rho }_{xx}\left({\mu }_{0}H\right)}^{\beta }$ with $\beta \sim 2.0$ is observed. (paper)