Thickness dependent structural and magnetic properties of ultra-thin Fe/Al structures

Abstract

The structural and magnetic properties of electron beam evaporated ultra-thin Fe/Al structures are studied as a function of Fe layer thickness, while keeping the Al layer thickness constant. The grazing incidence X-ray reflectivity measurements carried out on the structures having Fe layer thickness ≤20 A show substantial intermixing between the layers during deposition, indicated by a loss of periodicity. These structures resemble a composite single layer film consisting of Fe and Al clusters. However, for thicker Fe layers (≥30 A), the appearance of a first order Bragg peak in the reflectivity patterns indicates the formation of a better-multilayered structure. These results are also supported by AFM and resistivity measurements. The X-ray diffraction measurements show that in all the multilayer films, deposited Fe layers are textured mainly along (110) direction. The corresponding magnetic measurements show a soft magnetic behaviour of the films with an in-plane easy direction of the magnetization. The observed soft magnetic behaviour in these samples is explained in terms of (i) weak crystalline magnetic anisotropy due to small crystal grains and magnetostriction and (ii) the morphological and structural changes occurring due to the variation in the Fe layer thickness below the critical value in the deposited structures.