MAGNETIC DEPTH PROFILES IN STRAINED NICKEL-IRON THIN FILMS MEASURED BY POLARIZED NEUTRON REFLECTOMETRY. F. Ott and C. Fermon, Laboratoire Léon Brillouin, C.E.A./C.N.R.S Saclay, 91191 Gif sur Yvette CEDEX

Polarized neutron reflectivity with polarization analysis enables one to determine in-plane vectorial magnetic depth profiles. We investigated the modifications of the magnetostrictive properties of nickel and nickel-iron thin films due to relaxation strains at the substrate/film and film/vacuum interfaces. The in-plane magnetization rotation induced by a mechanical applied strain is shown to be non homogeneous throughout the layer. For a 100 nm iron-nickel thin film, the magnetization varies from 50deg. at the vacuum/film interface to 60deg. at the substrate(glass)/film interface. In a 40 nm nickel film, we observed that the magnetization rotation went up to 80deg. in the first 5 nm of the glass/nickel interface and decreased quickly to 34deg. in the rest of the layer.

Other measurements were made on trilayers systems Ni/NiFe/Ni and Ni/Ag/NiFe in order to observe the magnetic coupling between the layers. The magnetic alloys were chosen in order to have magneto-elastic constants of opposite signs so that the rotation directions induced by a strain are perpendicular for the two alloys. The Ni/NiFe/Ni system is shown to have a rather homogeneous magnetization whereas the Ni/Ag/NiFe trilayer exhibits magnetic rotation gradients in both layers.