  Using spin polarized neutron reflectivity experiments, we demonstrate an
unusual proximity behaviour when the superconductor (SC) and the ferromagnet
(FM) are coupled through an insulator (I) in YBa2Cu3O7-{\delta} (SC)/SrTiO3
(I)/La0.67Sr0.33MnO3 (FM) heterostructures. We have observed an unexpected
magnetic modulation at the interface region of the FM below the superconducting
transition temperature. The magnetization of the FM layer at the I/FM interface
was drastically reduced as compared to the magnetization in the rest of the FM
layer. This result indicates that the Cooper pairs tunnel across the insulator
and interact with the local magnetization at the interface region (extending ~
30 {\AA}) of the FM causing modification of the magnetization at the interface.
This unexpected magnetic behavior cannot be explained on the basis of the
existing theoretical models. However, the length scale associated here clearly
suggests the long range proximity effect as a result of tunneling of Cooper
pairs.
