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ALLOYS DIFFUSION ENERGY EVOLUTION Fe-Pt FE/PT MULTILAYERS FEPT MAGNETIC-PROPERTIES multilayers ORIENTATION reflectivity SPINODAL DECOMPOSITION SUPERLATTICES THIN-FILMS X-ray diffraction X-RAY-DIFFRACTION
Abstract:
Fe/Pt multilayers with modulation periods Lambda=24.1 +/- 0.2 and 37.2 +/- 0.1 A and [110]parallel to[111] bcc-fcc texture were fabricated by magnetron sputtering on thermally oxidized Si wafers. The structural evolution of the multilayers with annealing temperature in the range of 300-600 K was studied by in situ x-ray diffraction (XRD) and x-ray reflectivity. Two temperature regimes were found from the XRD data. Below 534 +/- 4 K slow, short-range diffusion is observed without significant broadening of the satellite peaks or changes in the texture. Above 534 K fast, long-range diffusion is observed accompanied by significant broadening of the satellites and rapid increase of the misorientations of the grains. The multilayers crystallize at about 583 K into the tetragonal FePt phase with a small degree of ordering and strong [111] texture. The transition resembles a first-order phase transition with a critical exponent beta=0.48 +/- 0.01 which practically does not depend on Lambda. The bulk interdiffusion coefficient, determined from the decay of the -1 satellite of the (001) Bragg peak of the multilayers, can be expressed in Arrhenius form as D(T)=(1.37 +/- 0.26)x10(-6) exp(-1.7 +/- 0.6/k(B)T) m(2)/s. The gradient-energy coefficient k, entering the Cahn-Hilliard diffusion equation [Acta Metallurg. 9, 795 (1961), 10, 179 (1962); J. Chem. Phys. 28, 258 (1959)], was estimated from the Lambda dependence of the diffusion coefficient to be (-6.8 +/- 0.2)x10(7) eV/cm. (c) 2006 American Institute of Physics
