ANGULAR MAGNETORESISTANCE PROVIDES TEXTURE INFORMATION ON HIGH-TC CONDUCTORS

Angular magnetoresistance measurements are performed by rotating a superconductor to an angle-theta in a fixed magnetic field, while monitoring the resistance R. It is argued theoretically that for fields well above the lower critical field, H much greater than H(cl), the bulk resistivity of the conductor is independent of theta if the crystallites of which it is composed are randomly oriented. Non-random orientation (a key aspect of texture) is revealed, therefore, by variations of R with theta. Dips in R indicate that the field is parallel to the copper oxide planes in a significant fraction of the current-carrying crystallites. C-axis, a-axis, and other textured film conductors are used to illustrate the technique. The angular magnetoresistance is found to be an important supplement to conventional texture determinations by microscopy and X-ray diffraction.