Structure of magnetic thin films and nanostructures studied by extended X-ray absorption fine structure

Thin magnetic films deposited on single-crystal substrates have been the su bject of numerous studies during the last decade. Their bidimensional chara cter, together with the occurrence of singular crystallographic structures, often confer to these thin films electronic properties that cannot be foun d in bulk solids. For example, thin nickel layers deposited on Cu(001) are found to present a perpendicular magnetic anisotropy in a very wide thickne ss range. We show that this can be explained by a distorted structure of ni ckel, originating from the strain induced by the epitaxy on the copper subs trate. In this field of two-dimensional magnetism, nanostructures with a re duced lateral dimension are also investigated. Thin iron layers on MgO(001) were cut into stripes by the 'atomic saw' method: a compression of the sub strate induces a dislocation slipping which saws both the substrate and the iron film into regular and separated ribbons. The easy magnetisation axis observed perpendicular to the stripes can be explained by a structural rela xation occurring during the structuring process. From these two studies, we see that the structure of films can be described as an elastic deformation of the bulk structure. (C) 2000 Elsevier Science B.V. All rights reserved.