Crystallization behavior of evaporated Gd-Fe alloy films

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Abstract
The composition dependence of the as-deposited structure, the in situ crystallization sequences, and thermal stability were investigated for evaporated Gd-Fe alloy films. The composition dependence of the structural variations in the as-deposited alloy films, the glass forming range, and the crystal size variation in the microcrystalline regions are consistent with the predictions of a model using hard spheres of two different sizes. The in situ crystallization reaction of Gd-Fe alloy films was characterized by the three reaction stages. (1) α-Fe and α-Gd were precipitated by the primary crystallization. The growth of primary crystals is characterized by a continuous process. (2) Some intermetallic compounds were formed by a polymorphous reaction. The growth of these phases is characterized by a discontinuous process. (3) The equilibrium phases are formed by decomposition reaction which was not detected in this study. The Gd atom array in the amorphous structure is concluded to be similar to the Fe atoms array of tetrahedra connected at corners. The thermal stability of the amorphous structure is the highest and growth rate of the primary crystals is the lowest at around 33 at. % Gd which is the composition of the close packed cubic Laves phase.