Temperature dependence of the Hall angle in single-crystal YBa2(Cu1-xCox)3O7- delta.

Abstract

We report measurements of the Hall coefficient (${\mathit{R}}_{\mathit{H}}$) and a-b-plane resistivity \ensuremath{\rho}(T) of cobalt-doped ${\mathrm{YBa}}_{2}$(${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$${)}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystals (0\ensuremath{\le}x\ensuremath{\le}0.096) from 20 to 400 K. Co doping gives rise to an unusual downward curvature in \ensuremath{\rho}(T) while the inverse Hall coefficient [1/${\mathit{R}}_{\mathit{H}}$(T)] also becomes nonlinear. Despite this, Anderson's formula for the Hall angle ${\mathrm{\ensuremath{\theta}}}_{\mathit{H}}$, namely, cot${\mathrm{\ensuremath{\theta}}}_{\mathit{H}}$=${\mathit{AT}}^{2}$+B continues to remain valid. In contrast to Zn, doping with Co decreases A while B remains constant. A simple model involving a square Fermi surface with rounded corners that could also account for the ${\mathit{AT}}^{2}$+B law is proposed.