title: Observation of reduced activation energy and the possible existence of decoupled pancake vortices in superconductor/ferromagnet bilayers.
abstract: Investigations of different superconducting (S)/ferromagnetic (F) heterostructures grown by pulsed laser deposition reveal that the activation energy (U) for the vortex motion in a high T(c) superconductor is reduced remarkably by the presence of F layers. The U exhibits a logarithmic dependence on the applied magnetic field in the S/F bilayers suggesting the existence of decoupled two-dimensional (2D) pancake vortices. This result is discussed in terms of the reduction in the effective S layer thickness and the weakening of the S coherence length due to the presence of F layers. In addition, the U and the superconducting T(c) in Y Ba(2)Cu(3)O(7 - δ)/La(0.5)Sr(0.5)CoO(3) bilayers are observed to be much lower than in the Y Ba(2)Cu(3)O(7 - δ)/La(0.7)Sr(0.3)MnO(3) ones. This in turn suggests that the degree of spin polarization of the F layer might not play a crucial role for the suppression of superconductivity due to a spin polarized induced pair-breaking effect in S/F bilayers.
authors.affiliation: Department of Physics, Indian Institute of Science, Bangalore, India. debphy@physics.iisc.ernet.in
authors.forename: D
authors.initials: D
authors.lastname: Samal
authors.forename: Chanchal
authors.initials: C
authors.lastname: Sow
authors.forename: P S Anil
authors.initials: PS
authors.lastname: Kumar