Magneto-resistance and vortex phase diagram of BaNi_0.1Fe_1.9As₂ single crystal

The transition from vortex glass to a liquid phase is studied in BaNi_0.1Fe_1.9As₂ single crystal with T_c=19.4 K by magneto-resistance measurements. The resistivity curves are measured in magnetic fields in a range of 0 T–13 T for H‖c and H⊥c. Good scalings for all values of resistivity ρ(H,T) and the effective pinning potential U₀(H,T) are obtained with the modified vortex glass theory by using the critical exponents s and H₀. Phase diagrams for H‖c and H⊥c are determined based on the obtained vortex glass temperature T_g, the vortex dimensionality crossover temperature T^*, and the upper critical magnetic field H_c2. Our results suggest that both below and above 5 T, single vortex pinning co-exists with collective creep, and collective creep is dominant. There is a narrower vortex liquid region for H⊥c than for H‖c in the vortex phase diagram, which may originate from a stronger pinning force.