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Sputtered Fe/Tb multilayers of various Fe and Tb thicknesses ͑0.22рt Fe р3.3 nm, 0.2рt Tb р1.9 nm͒ have been investigated by x-ray diffraction, Mössbauer spectrometry, and magnetic measurements in the 4.2-300 K temperature range. A compositionally modulated structure is shown with the appearance of pure amorphous iron in the center of the Fe layers thicker than 1.2 nm. When the Fe layers are thick enough ͑у2.2-2.4 nm͒, the Fe layers will crystallize. The magnetic properties ͑M ,T comp ,T c ,...͒ were analyzed in relation with Fe and Tb thicknesses and also with mean Tb composition. In agreement with the structure, the departure of magnetic properties from those of the corresponding amorphous alloys is observed when pure amorphous iron appears in the center of the layers. The dependence of the magnetic anisotropy axis on temperature and thicknesses is interpreted taking into account the composition modulation in the multilayers and the dominant magnetic subnetwork.

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Fe layers, 3, 6, 10, and 25 nm thick, were epitaxially deposited by ion-beam sputtering on InGaAs∕InP(100) wafers. For the 3-nm-thick layer, the sample shows a strong in-plane uniaxial magnetic anisotropy along the [110] direction between 5 and 300 K. The 6-nm film exhibits competition between the uniaxial magnetic anisotropy and the magnetic anisotropy of the bulk bcc Fe. The fourfold magnetic anisotropy of the bulk Fe dominates for the 10-nm Fe film. A decrease of the magnetization is observed for the thinner sample as compared to the bulk. This decrease is discussed in terms of Fe thickness, interface effect, diffusion effect, and possible phases at the interface with the semiconductor.