Sub-50 nm planar magnetic nanostructures fabricated by ion irradiation

He+ ion irradiation of Co-Pt multilayers through a silica mask obtained by a combination of high resolution lithography and reactive ion etching can produce an optical contrast-free, entirely planar, sub-50 nm magnetically patterned array. Furthermore, the specificity of magnetization reversal in such arrays leads to a weak dispersion of coercive forces. The technique holds promise for both present hard disk technology and future near field magneto-optical recording. (C) 1999 American Institute of Physics. [S0003-6951(99)01322-4].