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Spatially-resolved nonlinearity measurements of YBa2Cu3O7 bicrystal grain boundaries

Summary: Spatially-resolved nonlinearity measurements of YBa2Cu3O7 bicrystal
grain boundaries
Sheng-Chiang Lee and Steven M. Anlagea)
Center for Superconductivity Research, and Materials Research Science and Engineering Center,
Department of Physics, University of Maryland, College Park, Maryland 20742-4111
Received 2 October 2002; accepted 22 January 2003
We have developed a near-field microwave microscope to locally excite a superconducting film and
measure second- and third-order harmonic responses at microwave frequencies. We study the local
nonlinear response of a YBa2Cu3O7 thin film grown on a bicrystal SrTiO3 substrate. The location
of the bicrystal grain boundary is clearly identified by the microscope through higher harmonic
response, and the spatial resolution is on the order of the magnetic loop diameter, about 500 m. The
harmonic power and spatial resolution are modeled with a one-dimensional extended Josephson
junction simulation. From the model, the second-order harmonic response is dominated by
Josephson vortex generation and flow. A geometry-free nonlinear scaling current density JNL
is also extracted from the data, indicating that the grain boundary weak link is
the dominant nonlinear source in this case. 2003 American Institute of Physics.
DOI: 10.1063/1.1561152


Source: Anlage, Steven - Center for Superconductivity Research & Department of Physics, University of Maryland at College Park


Collections: Materials Science