Superconducting properties and hydrostatic pressure effect on ABi3 (A=Ba,Sr) single crystals
Abstract
We report on the crystal growth and characterization of ABi3 (A=Ba,Sr) superconductors. Single crystals of both compounds were grown by the self-flux technique. BaBi3 crystallized in a tetragonal structure with space group P4/mmm and SrBi3 in a cubic structure with space group Pm-3m. Superconductivity at Tc = 6.0 K for BaBi3 and Tc = 5.6 K for SrBi3 have been confirmed through dc magnetic susceptibility and electrical transport measurements. The dc magnetic susceptibility under hydrostatic pressure shows a positive pressure coefficient of dTc/dP = 1.22 K/GPa for BaBi3 and a negative pressure coefficient of dTc/dP = -0.48 K/GPa for SrBi3. The normal state electrical resistivity shows that both compounds are highly metallic in nature. The upper critical fields Hc2 evaluated by resistivity under magnetic fields (T,H) are 22 kOe for BaBi3 and 2.9 kOe for SrBi3. A specific heat jump of Ce/γ Tc = 1.05 suggests weak coupling superconductivity in BaBi3, whereas Ce/γ Tc = 2.08 for SrBi3 is higher than the BCS theory value of 1.43, indicating a strong coupling superconductor.