UNIAXIAL MAGNETIC-ANISOTROPY OF THIN EPITAXIAL FE FILMS NANOSTRUCTURED BY THE ATOMIC SAW METHOD

The 'atomic saw' method, initially developed for semiconductor heteros tructures, has been successfully used to cut an iron thin film, epitax ially grown onto a (001)MgO substrate, into stripes (1 mu m-100 nm lar ge and 8-1 nm high) or boxes (whose in-plane dimension ranges from 1 t o 3 mu m). A structural analysis by atomic force microscopy (AFM) of t he created magnetic nanostructures demonstrates the efficiency of this simple method and reveals that their geometries are controlled by the choice of the plastic strain. Magneto-optical study of films cut into stripes exhibit a surprisingly strong uniaxial magnetic anisotropy wi th the in-plane easy axis perpendicular to the stripes. This strong an isotropy (ranging from 8 x 10(5) to 14 x 10(5) erg/cm(3)) can be expla ined by a uniaxial relaxation of the elastic strain field. Magnetic st udies on boxes reveal that the cubic magnetocrystalline energy is reco vered since, in this case, the 'atomic saw' method acts in a biaxial w ay in the layer plane. Magnetization reversal, contrary to the case of a continuous epitaxial Fe film characterized by rapid displacement of 180 and 90 domain walls, is now governed by nucleation process. (C) 1 998 Elsevier Science B.V. All rights reserved.