Proximity effects in superconductor ferromagnet hybrid nanodevices

• Main Author: Jenkins, Alex Steven
• Published: University of Leeds 2010
• Subjects: 620.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555918

The effect of a single well characterised domain wall in ferromagnet/superconductor bilayers has been studied. Both vortex and transverse domain walls were investigated in Py/Nb systems. It was found that the stray field produced by both vortex and transverse domain walls will act to suppress the superconducting order parameter, although the nature of this suppression varies between the domain wall types. The out of plane core of a vortex domain wall causes a pronounced suppression in the properties of the superconductor, with the magnitude of the effect varying upon the exact position of the central core of the domain wall. The transverse domain I wall caused a suppression which had a pronounced current dependence, due to the stray field acting laterally across the superconductor. The effect of the domain wall was measured by monitoring the change in critical temperature, critical current and magnetoresistance of the S layer with and without a domain wall present. Attempts were made to trap a single domain wall in Co and Co/Ru/Co systems, but these were hindered by nucleation of domain walls at the rough edges and defects. The interface between the Py and Nb was altered to both enhance and suppress the electronic proximity effect, with the introduction of a Pd spacer layer giving rise to pronounced and controllable enhancements in the critical current at the edge of a vortex domain wall. This is the first study to measure the effect of a single domain wall and observe how this effect changes depending upon the magnetic/superconducting interface.