Ferromagnet/superconducting YBa2Cu3O7−δ bilayer devices

A magnetic fringe-field effect has been investigated for a simple bilayer device structure consisting of a Co0.9Fe0.1 film and an epitaxial YBa2Cu3O7−δ (YBCO) film patterned as a microbridge. The resistance of the bridge is measured with a four-probe technique and is found to depend on the orientation of a magnetic field, which is externally applied in the device plane. A maximum (minimum) of the resistance occurs when the magnetic field is applied in parallel (perpendicular) to the bridge axis. The difference between the maximum and the minimum is very large for a small range of temperature below the critical temperature of the YBCO film. The observed features in the resistance are qualitatively explained by vortex motion in the YBCO bridge under the influence of the magnetic fringe-field of the Co0.9Fe0.1 film.