Appearance of an inhomogeneous superconducting state in La{0.67}Sr{0.33}MnO{3}-YBa{2}Cu{3}O{7}-La{0.67}Sr{0.33}MnO{3} trilayers

An experimental study of proximity effect in La{0.67}Sr{0.33}MnO3 - YBa2Cu3O7 - La{0.67}Sr{0.33}MnO3 trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I_c) as the thickness of La{0.67}Sr{0.33}MnO3 layers (d_F) is scanned from ~ 50 A to ~ 1100 A. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures, this observation suggests a long range proximity effect in the manganite, modulated by it's weak exchange energy (~ 2 meV). The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d_F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.