Study of the magnetism and the magnetic anisotropy of Fe layers in Ni/Fe/Ni(111) by Mössbauer spectroscopy

Abstract The hyperfine field and the magnetic anisotropy of a Fe layer as a function of thickness have been investigated in several Ni/57Fex/Ni(1 1 1) trilayers with relatively thick Ni layers by Mossbauer spectroscopy. For Fe layers with thickness below 16 A, the Mossbauer spectra show always the presence of two ferromagnetic phases with high-spin state. In the range between 6 and 8 A, also a ferromagnetic phase with low-spin state and a paramagnetic phase have been found. The evolution of the mean hyperfine field of the 57Fe nuclei is used to study the Fe growth. A structural FCCBCC phase transition is found to begin with an iron thickness of 8 A. The easy direction of the magnetization is found out-of-plane for Fe interlayer with FCC structure, and perfectly in plane for Fe interlayer with BCC structure.