Om. Froehlich et al., INPLANE PENETRATION DEPTH OF HIGH-TEMPERATURE SUPERCONDUCTORS WITH SINGLE AND DOUBLE CUO LAYERS, Europhysics letters, 36(6), 1996, pp. 467-472
A dc technique based on the measurement of the magnetic-field dependen
ce of the critical current of bicrystal grain boundary Josephson junct
ions (GBJs) is used to precisely determine the temperature change Delt
a lambda(ab)(T) = lambda(ab)(T) = lambda(ab)(0) of the in-plane London
penetration depth of YBa2Cu3O7-delta (YBCO) and La1.85Sr0.15CuO4-delt
a (LSCO) thin films. The resolution of the applied measuring technique
is better than 0.2 Angstrom and the measured dependences are not sens
itive to extrinsic influences. Over a wide temperature range the data
obtained for different high-temperature superconductors confirm with h
igh accuracy the theoretical prediction for a d(x)2(-y)2-symmetry of t
he superconducting order parameter. The same temperature dependence is
measured for materials with single and double CuO layers.