Development of interface-induced out-of-plane magnetic anisotropy in Ni/Fe/Ni trilayers

The magnetic properties of trilayers Ni(1000 Å)/57Fe(x Å)/Ni(200 Å) grown by evaporation in ultra-high vacuum, have been investigated using Mössbauer spectroscopy, magneto-optic Kerr vector-magnetometry, and magnetic force microscopy (MFM). The data measured from a sample with Fe thickness x=6 Å show the development of an out-of-plane anisotropy that tends to align the magnetization of the 57Fe at about 40° respect to the normal to the layer plane. For higher 57Fe layer thickness the data indicate that the magnetization lies in the film plane. The magneto-optic measurements and the MFM images demonstrate also that when x=6 Å the 57Fe layer induces a reorientation of the magnetization of the Ni outermost layer from in-plane to out-of-plane. The results are interpreted as due to anisotropy effects induced at the interface Fe/Ni and to the γ→α transition that takes place between 6 and 16 Å.