Studies of the Anomaly of Hall Coefficient in High Tc Superconducting Thin Films

Measurements of the Hall coefficient (RH) were carried out for a polycrystalline YBa2Cu3O7-y film, a well oriented YBa2Cu3O7-y film and an oriented GdBa2Cu3O7-y film. Sign change of RH was observed for the two YBa2Cu3O7-y films near Tc, but not for the GdBa2Cu3O7-y film which contains partly the component of (110) orientation. The RH anisotropy model proposed previously turns out to be incorrect. Why the YBa2Cu3O7-y films experience sign change of RH while the GdBa2Cu3O7-y film does not is tentatively investigated.