Magnetic nanoconstrictions made from nickel electrodeposition in polymeric bi-conical tracks: Magneto-transport behavior

• Single nanoconstriction per magnetic wire is obtained by bi-conical track etching and electrodeposition.
• Magnetoresistance measurements at various angles result in irreversible jumps.
• Resulting jumps of magnetization have been attributed to the pinning and depinning of a constrained magnetic domain wall.

In a cylindrical magnetic nanowire, a magnetic domain wall (DW) can move along the wire when an applied magnetic field or a spin-polarized current is applied. We show that in a magnetic device composed of two conical nanowires connected by a nanosized constriction, a DW can be trapped and detrapped. The magnetoreistance and the relaxation processes of the DW exhibit a specific behavior. Such a device has been fabricating by Ni electrodeposition in bi-conical tracks polymer membrane made of Swift Heavy Ions bombarded poly(VDF-co-TrFE) copolymer and poly(ethylene terephtalate) PET thin films. The latter method allows to monitor the conicity of the bi-conical wires and to give access to a panel of very well-defined structures.