Abstract
Phase pure samples of LaOBiS2 and LaO0.5F0.5BiS2 are synthesized by conventional solid state reaction route via vacuum encapsulation technique at 800°C for 12h. Both the samples are crystallized in tetragonal P4/nmm space group with lattice parameters a=4.066(1)Å, c=13.862(4)Å for LaOBiS2; a=4.069(5)Å, c=13.366(2)Å for LaO0.5F0.5BiS2. Bulk superconductivity is confirmed in LaO0.5F0.5BiS2 with superconducting transition temperature (Tc) of 2.7K by DC magnetization and resistivity measurements. The isothermal magnetization (M–H) measurement shows closed loops with clear signatures of flux pinning and irreversible behavior. The magneto-transport ρ(T,H) measurements show resistive broadening and decrease in Tc (ρ=0) to the lower temperature with increasing magnetic field. The magnetic phase diagram involving upper critical and irreversibility fields as a function of temperature has been ascertained. The upper critical field Hc2(0) is estimated to be ∼19kOe corresponding to a Ginzburg–Landau coherence length of ∼130Å.
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