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

We have developed an irradiation technique that allows us to tune the magnetic 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 reflectometry, we study how irradiation-induced structural modifications correlate with magnetic properties. We also report the Ll(0) chemical ordering of FePt by irradiation at 280 degreesC. and the consequent increase of magnetic anisotropy. Planar magnetic patterning at the sub 50 nm scale can be achieved when the irradiation is performed through a mask. New magnetic behaviors result from the fabrication process. They appear to arise from collateral damage. We model these effects in the case of SiO2 and W masks. The planarity of irradiation-induced patterning and its ability to independently control nanostructure size and coercivity make it very appealing for magnetic recording on nanostructured media. Finally, possible applications to the granular media used in current hard disk drive storage technology are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.