With progress in nanofabrication, new strategies have become available that allow precise control of nanoscale optical fields using metallic nanostructures. Here we review recent progress in the control of optical resonances in metal nanostructures for applications in sensing and spectroscopy. We discuss the use of new techniques, such as helium-ion beam milling, which allow precise sculpting of nanometer-scale gaps; new materials such as metal oxides, which have a response somewhere inbetween that of conventional dielectrics and noble metals; and new designs such as L-shaped gap antennas which allow controlling the polarization state of light through near-field interactions between closely spaced antennas.
We report a reproducible top down fabrication procedure for a single domain wall magnetoresistance H-shaped device. A
bi-layer e-beam lift-off process is used and the e-beam exposure dose sensing technique and proximity effect correction
are discussed, together with a method to reduce the alignment tolerance to below 20 nanometer. The domain wall width
is constrained down to 37nm and room temperature domain wall magnetoresistance ratio of 0.3% was detected. The
dependence of switching magnetic field to domain width will be discussed, as well as the maximum domain width which
can retain its magnetisation aligned along the long axis at zero field which is found to be 210nm in our experiment.