Fabrication of nanoscale magnetic ring structures and devices

We have fabricated nanoscale ferromagnetic rings and radially contacted magnetic ring structures using electron beam lithography with a lift-off process for pattern transfer. The resist thickness and electron beam dose were optimised to produce 10 nm-thick permalloy rings with linewidths of 30 nm and outer diameters down to 90 nm. Magneto-optical Kerr effect measurements show that down to the smallest diameters, reproducible magnetic switching into the flux-closure vortex state is maintained. For the radially contacted ring devices, magnetic rings with linewidths of 100 and 200 nm (outer diameters of 1.1 and 1.2 mum) were produced and aluminium contacts added using an electron beam writer overlay procedure. The position of domain walls could be determined by measuring the magnetoresistance between different contacts and so the details of the magnetic switching could be ascertained. (C) 2004 Elsevier B.V. All rights reserved.