Highly ordered porous membranes for fabrication of multilayered nanostructures with perpendicular magnetic anisotropy

Abstract In this research, we describe the technology of fabrication of double-sided nanoporous alumina membranes with an ordered pore arrangement, adjustable pore size and smoothed surface relief, which allows maintaining the perpendicular magnetic anisotropy (PMA) of [Co/Pd] multilayers deposited over them. Their fabrication includes several important technological processes, namely two-step anodization of aluminum foil and subsequent ion-beam etching, which together allow for effective control of the morphology of the formed membranes. It is demonstrated that the adjustability of the anodization process allows for the control of the basic characteristics of the porous structure of the membrane, including cell and pore size, as well as its properties, including its flexibility and transparency, through alteration of the voltage and selection of an appropriate electrolyte. Simultaneously, ion-beam treatment is able to modify significantly the surface relief of membranes that facilitates their adaptation to the requirements of potential applications. The implemented transfer of the uniform porous morphology from the membrane to the deposited film accompanied by the conservation of PMA of the latter opens up opportunities of creating nanostructured magnetic media on porous alumina membranes which can be applicable in flexible spintronic devices.