Fabrication and magnetisation measurements of variable-pitch gratings of cobalt on GaAs

A technique for engineering micron and sub-micron scale structures from magnetic films of transition metals has been developed using a combination of electron and ion beam lithography. The pattern is defined by a mask produced by 60kV electron beam lithography, enabling near-vertical sidewalls to be produced. The focused ion beam is rastered to etch cobalt in the mask openings. PMMA and aluminium masks have been assessed. High quality arrays of magnetic Co wires have been fabricated on GaAs substrates. This processing is adaptable to the fabrication of novel devices from a variety of metal combinations which would not be possible by the usual lift-off metallisation route. An artificial shape anisotropy is observed in the magnetic properties of gratings of width ≈0.5μm and separation 0.5μm fabricated from a 50nm thick Co film, resulting in a demagnetising field of ≈0.8kØe.