Experimental test of the ${\mathit{T}}^2$ law for the Hall angle from ${\mathit{T}}_{\mathit{c}}$ to 500 K in oxygen-reduced ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{6+\mathit{x}}$ crystals

In both ‘‘90-K’’ and ‘‘60-K’’ ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6+\mathit{x}}$ crystals, we find that the ${\mathit{T}}^2$ law for the Hall angle, measured with field H∥c, remains valid for temperatures T between ${\mathit{T}}_{\mathit{c}}$ and 500 K. The persistence of power-law behavior over this wide range is not affected by oxygen reduction. In contrast to this anomalous behavior, the Hall coefficient observed with H⊥c is negative and temperature independent. Measurements of the in-plane resistivity ${\mathrm{\rho }}_{\mathit{x}\mathit{x}}$ to 500 K disclose the existence of a kink temperature ${\mathit{T}}_{\mathit{K}}$ (∼320 K) that separates a high-temperature power-law regime from a low-temperature region in which ${\mathrm{\rho }}_{\mathit{x}\mathit{x}}$ displays significant curvature.