Beam-induced magnetic property modifications: Basics, nanostructure fabrication and potential applications

We have developed an irradiation technique that allows us to tune the magne tic properties of thin films without affecting their roughness. We discuss the mechanisms involved and the applications. He+ ion irradiation of Co/Pt multilayers lowers their magnetic anisotropy in a controlled way, reducing the coercive force and then leading to inplane magnetization. By X-ray refl ectometry, we study how irradiation-induced structural modifications correl ate with magnetic properties. We also report the Ll(0) chemical ordering of FePt by irradiation at 280 degreesC. and the consequent increase of magnet ic anisotropy. Planar magnetic patterning at the sub 50 nm scale can be ach ieved when the irradiation is performed through a mask. New magnetic behavi ors result from the fabrication process. They appear to arise from collater al damage. We model these effects in the case of SiO2 and W masks. The plan arity of irradiation-induced patterning and its ability to independently co ntrol nanostructure size and coercivity make it very appealing for magnetic recording on nanostructured media. Finally, possible applications to the g ranular media used in current hard disk drive storage technology are discus sed. (C) 2001 Elsevier Science B.V. All rights reserved.