The Influence of $He^+$ Ion Bombardment on Magnetic Properties of NiFe/Au/Co/Au Multilayers

The influence of $He^+$ ion bombardment on magnetoresistance, magnetization reversal and domain structure of sputtered $(Ni_{80}Fe_{20}(2 nm)//Au(2 nm)//Co(0.6 nm)//Au(2 nm))_{10}$ multilayers was investigated. The samples were bombarded using $He^+$(30 keV) ions with fluences D varied from $10^{13}$ to 3×$10^{16}$ $He^+$/$cm^{2}$. With increasing D the following changes in magnetic properties were observed: (i) exponential decay of the saturation field of Co layers, (ii) progressive decrease in magnetoresistance as a result of degradation of Co layers perpendicular anisotropy, (iii) linear decrease in stripe domain period with log(D).