Imprinting superconducting vortex footsteps in a magnetic layer.

Jérémy Brisbois,Pierre Colson,Thibaut Devillers,Savita K P Veerapandian,Roman B G Kramer,Gorky Shaw,Ngoc Duy Nguyen,Wilson A Ortiz,Jonathan I Avila,Maycon Motta,Nora M Dempsey,Alejandro V Silhanek,Benoît Vanderheyden,Philippe Vanderbemden

doi:10.1038/srep27159

Abstract

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit cards and computer hard drives. Here we experimentally show that a similar principle can be applied for imprinting the trajectory of quantum units of flux (vortices), travelling in a superconducting film (Nb), into a soft magnetic layer of permalloy (Py). In full analogy with the magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py board. The mutual interaction between superconducting vortices and ferromagnetic domains has been investigated by the magneto-optical imaging technique. For thick Py layers, the stripe magnetic domain pattern guides both the smooth magnetic flux penetration as well as the abrupt vortex avalanches in the Nb film. It is however in thin Py layers without stripe domains where superconducting vortices leave the clearest imprints of locally polarized magnetic moment along their paths. In all cases, we observe that the flux is delayed at the border of the magnetic layer. Our findings open the quest for optimizing magnetic recording of superconducting vortex trajectories.

Highlights

Vortex-antivortex lattices can be spontaneously induced[16,17] when cooling down in zero applied field below the superconducting critical temperature Tc
The investigated hybrid system is composed of a Py (Fe19Ni81) polygonal-shaped layer (F) of three different thicknesses t = 50 nm, 100 nm and 460 nm, deposited on top of a 140 nm-thick Nb film (S) of 2 × 2 mm[2]
The polygonal shape of the Py layer aims to explore different angles of penetration of the magnetic flux entering through the sides of the Nb square

Summary

Results and Discussion

When the temperature is increased up to 10 K and H is subsequently decreased to zero (Fig. 5(c)), we observe that smooth flux penetration in the Nb layer has left a clear imprint in the Py layer We expect to trigger further experimental and theoretical studies to discover new magnetic compounds optimizing the resolution of the technique down to single vortex imprints

Methods

Author Contributions

Additional Information