Amorphous and quasicrystalline AlMn and AlFe phase synthesis by ion beam mixing and related transport properties

Abstract

AlMn and AlFe multilayers have been mixed at various temperatures (450, 493 and 77 K) with 800 keV Xe + ions. The mixing stages as a function of dose at various temperatures and the nature of the synthesized phases have been characterized using three complementary techniques: Rutherford backscattering spectrometry (RBS) to observe the spatial distribution resulting from the mixing process at the interfaces; transmission electron microscopy (TEM) observations to determine the microstructures and phases; and conversion electron Mössbauer spectroscopy (CEMS) in the case of AlFe alloys for the study of local order evolutions. Mixing efficiency and nature of the elaborated phases depend on ion dose and temperature of the sample. A dose of about 3 × 10 16 ions/cm 2 is necessary to obtain homogeneous amorphous alloys at 77 K, while the quasicrystalline phases are formed at 450 K (AlMn) or 493 K (AlFe) for a dose of 8 × 10 15 ions/cm 2. In the AlFe alloys, the local environments of the Fe-atoms deduced from CEMS show different characteristic evolutions for amorphous and quasicrystalline phases with a combination of several sites the relative proportions of which vary at each intermediate mixing stage. Optical (reflectivity) and transport (resistivity, magnetoresistance) measurements performed on the homogeneous mixed films exhibit different electronic structures of the phases and different magnetic behaviors for AlMn (spin glass transition) and AlFe (weak localization).