Anisotropic Nature of Superconductivity in Hexagonal Rubidium Tungsten Bronze Rb(subscript 0.23)WO(subscript 3+δ)

L.C. Ting；J. J. Pan；T. W. Liao；H. H. Hsieh；F. Z. Chien；P. H. Hor；D. C. Ling

Chinese Journal of Physics

45卷2s2期（2007 / 04 / 01）

237 - 243

繁體中文

Low-field M(H), transport, and magnetization measurements have been performed on hexagonal rubidium tungsten bronze Rb0.23WO(subscript 3+δ). Various thermodynamic parameters, such as H(subscript c1)(0), H(subscript c2)(0), λ(subscript ab)(0),λ(subscript c)(0), ξ(0), anisotropy parameterτ, and Ginzburg-Landau parameterκ are reported. The irreversibility line H(subscript irr)(T) follows (1-T/Tc)(superscript n) with exponent n=1.51 for sample with δ~-0.10 and 2.11 for sample with δ~0.02, indicating that the vortex dimensionality of Rb0.23WO2.90 is anisotropic three-dimensional (3D) and that of Rb0.23WO3.02 is quasi two-dimensional (2D). In addition, the magnetization curves in high-field regime near T(subscript c) collapse onto a universal curve 4πM/(TH)β=F[A((TT(subscript c)(H))/(TH)β)]with exponent β=2/3 for sample with δ~-0.10 and 1/2 for sample with δ~0.02, indicative of an anisotropic 3D and a quasi-2D scaling behavior for Rb0.23WO2.90)and Rb0.23WO3.02, respectively. The observed results strongly suggest that oxygen content has a significant influence on the nature of the superconducting properties of Rb0.23WO(subscript 3+δ).