TEMPERATURE-DEPENDENCE OF THE HALL ANGLE IN SINGLE-CRYSTAL YBA2(CU1-XCOX)3O7-DELTA

We report the measurements of the Hall coefficient (R(H)) and a-b-plane resistivity rho(T) of cobalt-doped YBa2(Cu1-xCox)3O7-delta single crystals (0 less-than-or-equal-to x less-than-or-equal-to 0.096) from 20 to 400 K. Co doping gives rise to an unusual downward curvature in rho(T) while the inverse Hall coefficient [1/R(H)(T)] also becomes nonlinear. Despite this, Anderson's formula for the Hall angle theta(H), namely, cottheta(H) = AT2 + 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 AT2 + B law is proposed.