Dresden 2006 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 3: Thin film analysis I

DS 3.2: Vortrag

Montag, 27. März 2006, 10:15–10:30, GER 38

In-situ Study of the Thermal Stability of Fe-Pt Multilayers — •Nikolay Zotov, Jürgen Feydt, Alan Savan, and Alfred Ludwig — Forschungszentrum Caesar, Ludwig-Erhard-Allee 2, D-53175 Bonn

Annealing of Fe-Pt multilayers has attracted attention as a promising reaction pathway for the synthesis of FePt hard-magnetic thin films. Such nanostructures are possible candidates for high-density magnetic recording devices or exchange-spring magnets due to the very large magnetocrystalline anisotropy of the fct FePt phase. Fe-Pt multilayers with modulation periods 2.42 and 3.75 nm were fabricated by magnetron sputtering. Simulations of the high-angle satellites at room temperature revealed the presence of strong (111) texture, some Fe-Pt intermixing during the deposition and vertical grain sizes of about 16-24 nm. The structural evolution of the multilayers with temperature was studied by in-situ X-ray diffraction between 300 and 603 K. Two temperature regimes are established. Below 534 K a slow diffusion with coherent interfaces, no change of the texture and minor decrease of the lateral grain size of the multilayers is observed. Above 534 K, a fast diffusion causes incoherent variations of the modulation periods, increase of the vertical misorientations of the grains and significant changes of the lateral grain sizes, which might suggest the presence of grain boundary diffusion in the multilayers with small modulation period. Both multilayers transform at about 583 K into the fcc FePt phase. The phase transition is of first-order and a power law describes the order parameter with a critical exponent equal to 0.97(2), which is practically independent of the modulation period.