ANISOTROPY OF THE PENETRATION DEPTH IN YBA2CU3O7-DELTA - JOSEPHSON-TUNNELING STUDIES

The modulation of the Josephson critical current between two supercond uctors in a magnetic field provides a direct, low-field dc measurement of the penetration depth of the two superconductors. To measure the i n-plane penetration depth anisotropy of YBa2Cu3O7-delta, we have fabri cated low leakage Pb/Insulator/YBa2Cu3O7-delta tunnel junctions on det winned YBa2Cu3O7-delta single crystals with tunneling along the c axis . By applying the magnetic field along the b and a crystalline axes of YB(a)2Cu(3)O(7-delta) lambda(a) and b are extracted from the respecti ve field modulation patterns. We find a large anisotropy [(lambda(a)/l ambda(b))(2) greater than or equal to 2] of the penetration depths alo ng the a and b axes.