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We have systematically investigated the crystal structure and the magnetic properties of BiS2-based superconductor Ce1-xNdxO1-yFyBiS2 (x = 0 - 1.0, y = 0.3, 0.5 and 0.7) and Nd1-zSmzO1-yFyBiS2 (x = 0 - 0.8, y = 0.3, 0.5 and 0.7). In the REOBiS2 system, both crystal structure and physical properties are tunable by mixing the RE (RE = rare earth) site with Ce, Nd and Sm due to the difference of ionic radius of RE. In the Ce1-xNdxO1-yFyBiS2 system, bulk superconductivity is observed for x = 1.0 with y = 0.3 and x = 0.5 - 1.0 with y = 0.5. The transition temperature (Tc) increases with increasing Nd concentration. The highest Tc is 4.8 K for x = 1.0 with y = 0.5 in the Ce1-xNdxO1-yFyBiS2 system. By the Nd substitution for Ce, lattice contraction along the a axis is generated while the c axis does not show a remarkable dependence on Nd concentration. The lattice constant of c decreases with increasing F concentration. Furthermore, we found that the Nd site can be replaced by smaller Sm ions up to z = 0.8 in Nd1-zSmzO1-yFyBiS2. Bulk superconductivity is observed within z = 0 - 0.8 for y = 0.3 and z = 0 - 0.6 for y = 0.5. The Tc increases with increasing Sm concentration. The highest Tc is 5.6 K for z = 0.8 with y = 0.3. With increasing Sm concentration, the lattice constant of a decreases while the lattice constants of c does not show a remarkable dependence on Sm concentration. We found that the chemical pressure generated by systematic solution of the RE site in the blocking layer commonly induces lattice contraction along the a axis in Ce1-xNdxO1-yFyBiS2 and Nd1-zSmzO1-yFyBiS2. The obtained results indicate that both optimal F concentration and uniaxial lattice contraction along the a axis generated by chemical pressure are essential for the inducement of bulk superconductivity in the REO1-yFyBiS2 system.
We investigate the external hydrostatic pressure effect on the superconducting transition temperature (Tc) of new layered superconductors Bi4O4S3 and NdO0.5F0.5BiS2. Though the Tc is found to have moderate decrease from 4.8 K to 4.3 K (dTconset/dP =
We report the electrical resistivity measurements under pressure for the recently discovered BiS2-based layered superconductors Bi4O4S3 and La(O,F)BiS2. In Bi4O4S3, the transition temperature Tc decreases monotonically without a distinct change in th
We study the impact of hydrostatic pressure on superconductivity of new BiS2 based layered REO0.5F0.5BiS2 (RE-La, Pr, and Nd) compounds through the measurements of dc electrical resistivity. The REO0.5F0.5BiS2 (RE-La, Pr and Nd) compounds synthesized
We have successfully synthesized a new BiS2-based superconductor NdOBiS2 with F-doping. This compound is composed of superconducting BiS2 layers and blocking NdO layers, which indicates that the BiS2 layer is the one of the common superconducting lay
Pressure effect on superconducting properties of two YB6 samples (Tc = 5.9 and 7.5 K) were investigated by measurements of electrical resistivity, magnetic susceptibility, and X-ray diffraction in the pressure range up to 320 kbar. Magnetoresistivity