Spatial imaging of the critical current density in epitaxial Y ₁Ba₂Cu₃O₇ films

We report the first spatially resolved measurement of the critical transport current density of c-axis oriented epitaxial Y₁Ba ₂Cu₃O₇ films on 〈100〉 SrTiO ₃ using low-temperature scanning electron microscopy (LTSEM). The local critical current density, imaged with a spatial resolution of ∼1 μm, has been found to vary considerably in these films. Possible reasons for the observed spatial inhomogeneities are surface imperfections of the substrate and precipitates in the film. The spatial inhomogeneity of the critical current density in epitaxial films might be a reason for differences in the temperature dependences of the critical current density obtained by magnetic and transport measurements.