Reconfigurable superconducting vortex pinning potential for magnetic disks in hybrid structures.
High resolution scanning Hall probe microscopy has been used to directly visualise the superconducting vortex behavior in hybrid structures consisting of a square array of micrometer-sized Py ferromagnetic disks covered by a superconducting Nb thin film. At remanence the disks exist in almost fully flux-closed magnetic vortex states, but the observed cloverleaf-like stray fields indicate the presence of weak in-plane anisotropy. Micromagnetic simulations suggest that the most likely origin is an unintentional shape anisotropy. We have studied the pinning of added free superconducting vortices as a function of the magnetisation state of the disks, and identified a range of different phenomena arising from competing energy contributions. We have also observed clear differences in the pinning landscape when the superconductor and the ferromagnet are electron ically coupled or insulated by a thin dielectric layer, with an indication of non-trivial vortex-vortex interactions. We demonstrate a complete reconfiguration of the vortex pinning potential when the magnetisation of the disks evolves from the vortex-like state to an onion-like one under an in-plane magnetic field. Our results are in good qualitative agreement with theoretical predictions and could form the basis of novel superconducting devices based on reconfigurable vortex pinning sites.
Department of Physics, University of Bath, Bath, BA2 7AY, United Kingdom.
Estefani
E
Marchiori
Department of Physics, University of Bath, Bath, BA2 7AY, United Kingdom.
Peter J
PJ
Curran
School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.|Center for Biomolecular Nanotechnologies, Italian Institute of Technology, Genova, 16163, Italy.
Jangyong
J
Kim
School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.|ISIS Neutron and Muon Source, Didcot, OX11 0QX, United Kingdom.
Nathan
N
Satchell
School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.
Gavin
G
Burnell
Department of Physics, University of Bath, Bath, BA2 7AY, United Kingdom.
Simon J
SJ
Bending