Focused ion beam irradiation of ferromagnetic thin films in the presence of an applied field

A stage has been constructed to supply a variable strength in situ magnetizing field for use in a focused ion beam system. Ion irradiation experiments were performed in the presence of the magnetic field in order to investigate its effect on the localized exchange bias field in thin CoFe/IrMn bilayers. Squares with dimensions 10 x 10 μm2 were directly irradiated by Ga+ ions of energy 30 keV at doses between 1 x 1013 and 1 x 1015 ions cm-2. TEM studies of the magnetization reversal behaviour of the squares showed that bias field reversal could be achieved with the maximum achievable bias field strength being > 50% of that along the original direction