Determining the absolute value of penetration depth of large area films

We report a method that allows the measurement of the absolute size of the magnetic penetration depth lambda(T) of large area YBa2Cu3O7-delta films using the two-coil method where a YBa2Cu3O7-delta film is overlapped with a 1-mu m-thick Pb film equivalent in size placed in the gap between the drive and receive coil. The drive; coil has fewer counter turns on-the top section than the bottom, which is closer to the film, so the film's edge current would be suppressed and the accuracy that depends on geometry is greatly improved. The transition of the Pb film causes a steplike portion in the mutual inductance M(T) graph and the resultant step height leads to the absolute value of lambda. (C) 1996 American Institute of Physics.