Synthesis of Bi-Lu-substituted iron garnet films for visualization of magnetic flux in high-Tc superconductors

In order to visualize the magnetic flux that penetrates into high-T-c superconductors with high spatial resolution. opitaxial growth of the in-plane magnetic Bi-Lu-substituted iron garnet films was investigated. The ratio of increment.,, of Faraday rotation to magnetic field increased to -13deg/(cm.Oe) by Bi and Ga substitutions. The as-grown films showed a perpendicular magnetic anisotropy. The appropriate conditions for annealing treatments that change the perpendicular magnetic anisotropy into an in-plane magnetic anisotropy were investigated. Then. the annealed (BiLu)(3)(FeGa)(5)O-12 film clearly showed a high resolution image of the magnetic flux that penetrates into the NdBa2Cu3O7-delta high-T-c superconductor at temperatures between 5 K and 100 K. and the behavior of the magnetic flux penetrating the microcracks less than 5 mum in width was successfully captured; the magnetic flux depends on external magnetic field and temperature.