Strongly anisotropic electrical properties of single-crystal YBa2Cu3O7-x

Abstract

Crystals of orthorhombic, superconducting YBa2Cu3O7-x have been prepared. They are twinned in the nearly tetragonal ab plane. The resistivity and Hall effect have been measured in the normal state in the ab plane, the highly conducting plane of the Cu-O layers. We find that the resistivity in the ab plane, measured with currents exclusively in the plane, is strictly linear in temperature from room temperature down to the fluctuation regime near the superconducting transition. This result confirms previous less direct measurements in which the currents flowed in the much more resistive c direction as well. We find the Hall constant for the magnetic field parallel to c and the currents in the ab plane, to be p type and inversely proportional to temperature. This latter behavior is extremely unusual and unexplained, but similar to that found in polycrystalline YBa2Cu3O7-x material. It is in contrast to our previous result for the magnetic field in the ab plane. In that case, the Hall constant is n type and nearly temperature independent. Both the Hall effect and the resistivity demonstrate the extremely anisotropic nature of this system. © 1988 The American Physical Society.