Hall effect and resistivity of oxygen-deficient YBa2Cu3O7−δ thin films

Abstract

We report measurements of the ab-plane resistivity (ρ) and Hall coefficient (${\mathit{R}}_{\mathit{H}}$) of crystalline thin films of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ (0.05≤δ≤0.53) from below ${\mathit{T}}_{\mathit{c}}$ up to 400 K. In contrast to measurements on sintered samples, and some other recent work on thin films, the residual resistivity of these films (as extrapolated from high temperature) remains low for all δ. As oxygen is removed from the films, ρ increases and ρ(T) develops downward curvature below 300 K. The Hall angle (${\mathit{FTHETA}}_{\mathit{H}}$) however, continues to obey the relation, cot${\mathit{FTHETA}}_{\mathit{H}}$=${\mathit{AT}}^2$+B. As δ increases, the coefficient A decreases while B remains constant. Data for an oxygen-deficient single crystal of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ agree well with our film data. Measurements of ρ in the region of the superconducting transition in fields of up to 7 T, applied parallel to the crystallographic a, b, or c axes, are also reported. The well-known ‘‘field-induced broadening’’ of the ρ(T) curves becomes larger as δ is increased. There is evidence for a transition line in the field-temperature plane that has the 4/3-power-law behavior associated with critical fluctuations in the three-dimensional XY model.