On the structure and magnetism of Ni/Si and Fe/Si bilayers irradiated with 350-MeV Au ions

Modifications of Ni/Si and Fe/Si bilayers induced by swift heavy ions were studied in the regime Of pure electronic stopping. Poly-crystalline films, 65-75 nm thick, were deposited via electron evaporation (Ni) or pulsed laser deposition (Fe) onto Si wafers and irradiated at <= 300 K with 350-MeV Au26+ ions to fluences of up to 5 x 10(15) ions/cm(2). The samples were analyzed by Rutherford backscattering spectroscopy, X-ray diffraction and the magneto-optical Kerr effect. In the Fe/Si samples, a 20 nm Fe-57 layer was interlayed between Fe-nat and Si in order to monitor interface mixing and phase formation by means of Moessbauer spectroscopy. In both systems, a high mixing rate of approximate to 60 nm(4) was found, correlated with relaxation of the as-deposited stress and uniaxial magnetic anisotropy. At higher fluences, full interdiffusion gives rise to amorphous silicide phases, build-up of stress and loss of magnetic texture. (c) 2005 Elsevier B.V. All rights reserved.