Fabrication of curved-line nanostructures on membranes for transmission electron microscopy investigations of domain walls
We have fabricated curved-line ferromagnetic nanostructures on membranes for transmission electron microscopy investigations of the equilibrium magnetic spin configurations. The magnetic elements were fabricated using electron-beam lithography and a lift-off procedure for pattern transfer. Due to the fragile nature of the membranes, the design of the elements was chosen to ensure that the lift-off was possible without using ultrasound. The elements included three-quarter rings, zig-zag lines and wavy lines with notches resulting in constrictions with widths down to 30 nm. Magnetic configurations were observed using electron holography and Lorentz microscopy. In particular, the details of the spin structure of vortex and transverse walls, and its dependence on the local geometry were obtained. While Lorentz microscopy provided qualitative information about magnetic spin orientations and the positions of domain walls, electron holography gave quantitative high-resolution images of the magnetic induction allowing the direct measurement of the stray field between adjacent domain walls. (c) 2006 Elsevier B.V. All rights reserved.