  Single crystals of La_1.8Sr_0.2CuO_4-\delta grown by the travelling solvent
floating zone method have been ground to spherical shape for studies of
anisotropic supercondcucting properties by SQUID magnetometry. Here we report
on magnetization measurements parallel and perpendicular to the c-axis on two
of these crystals. At low enough temperatures and fields the spheres are
perfectly shielding (susceptibility -1.5 [SI]) and thus magnetically isotropic.
The field dependence of the critical temperature, the transition width and the
field expulsion well below T_c is qualitatively similar in both samples and is
detailed in the paper. The anisotropy of the first critical field also shows
similar behavior for the two crystals. Magnetization vs field experiments
reveal a large difference in the hysteresis behavior along the two directions
and an enhancement of the critical current density through the CuO_2-planes
compared to the in-plane current density at higher fields.

Superconductivity