DIRECT MAGNETOOPTICAL MEASUREMENTS OF ANISOTROPIC CRITICAL CURRENTS IN (LA1-XSRX)(2)CUO4 SINGLE-CRYSTALS

We report on measurements of the penetration of magnetic flux in singl e crystals of (La1-xSrx)(2)CuO4 as seen using the magnetic garnet imag ing technique. The technique measures the spatial and temporal depende nce of the magnetization by using a wafer of doped magnetic garnet mat erial placed in contact with the sample to be measured and imaged with an optical microscope. We have directly measured the critical current anisotropy in this system as a function of temperature and doping and found clear evidence for intrinsic pinning as well as a pronounced de pendence of the anisotropy on doping.