ANISOTROPY, PINNING, AND THE MIXED-STATE HALL-EFFECT

We have studied the mixed-state Hall effect of the high-T-c supercondu ctors Nd1.85Ce0.15CuO4(NCCO), Tl2Ba2CaCu2O8 (Tl2212), and YBa2Cu3O7 (Y BCO), and the isotropic low-T-c superconductor amorphous Mo3Si (a-Mo3S i). We demonstrate the pinning independence of the Hall conductivity s igma(xy) and its consequent scaling in terms of the anisotropy of NCCO , T12212, and YBCO. In YBCO and a-Mo3Si the Hall angle is enhanced as we reduce the effective pinning, yet sigma(xy) is unchanged. For all o f these materials there is a vortex contribution sigma(xy)-1/H at low fields while at high fields sigma(xy)similar to H. These results provi de evidence that beneath the effects of pinning and anisotropy a relat ively simple and universal behavior of the mixed-state Hall effect exi sts.