Photoinduced changes of the electrical anisotropy in oxygen-depleted YBa2Cu3Ox

Long-term photoexcitation experiments were performed on YBa2Cu3Ox (x approx imate to 6.6) thin films, prepared by pulsed-laser deposition on "tilted" S rTiO3 substrates. From the anisotropic resistance of the samples, the in-pl ane and the out-of-plane resistivities were calculated. Photoexcitation was carried out with a He-Ne laser at various temperatures from 70 K to 305 K. We observed that the electrical anisotropy rho(c)/rho(ab) increased at low temperatures, but decreased at high temperatures. This unusual behavior re sembles that of the in-plane Hall mobility in a previous study. Possible in terpretations according to the models for the photodoping effect In YBa2Cu3 Ox are discussed.