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

Abstract

Thin magnetic films deposited on single-crystal substrates have been the subject of numerous studies during the last decade. Their bidimensional character, together with the occurrence of singular crystallographic structures, often confer to these thin films electronic properties that cannot be found in bulk solids. For example, thin nickel layers deposited on Cu(001) are found to present a perpendicular magnetic anisotropy in a very wide thickness range. We show that this can be explained by a distorted structure of nickel, originating from the strain induced by the epitaxy on the copper substrate. In this field of two-dimensional magnetism, nanostructures with a reduced lateral dimension are also investigated. Thin iron layers on MgO(001) were cut into stripes by the ‘atomic saw’ method: a compression of the substrate 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 relaxation 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.