Text 2. The features of CoFeZr alloy nanocrystals formation in film composites of (CoFeZr)x(MgF2)100-x

Abstract The influence of relative content of the metal component on the phase composition and substructure of (CoFeZr)x (MgF2)100-x film nanocomposites between x = 7 ÷ 51 (at.%) has been established by X-ray diffraction (XRD), X-ray electron spectroscopy (XPS) and infrared spectroscopy (IR). Ion-beam sputtering of a composite target from Co45Fe45Zr10 amorphous alloy plate prepared micron-thick nanocomposite layers with MgF2 dielectric inserts in the argon atmosphere. The results show that at a relatively low content х 25, the MgF2 matrix becomes X-ray amorphous, and CoFeZr alloy nanocrystals of the hexagonal syngony based on the -Со structure with dimensions of about 10 nm are first formed; they are predominantly oriented in the plane of the hexagonal lattice (001). With a further increase of the metal alloy content up to х~40 in the region nearer to the percolation threshold, the crystal structure of nanocrystals of the CoFeZr alloy becomes a cubic phase based on -Fe with a preferred orientation of (110). XPS studies confirm the presence of a predominant type of metal bonds in clusters and nanocrystals of CoFeZr, despite the oxidation of the thinnest surface layers, as well as ionic bonds in the MgF2 dielectric matrix, preserved because of self-organization even in non-equilibrium conditions of ion-plasma sputtering. Two features on the curve of the dependence of the resistivity of nanocomposites on the alloy concentration are due to: the first one (x ~ 25) - the formation of nanocrystals of hexagonal symmetry from clusters of the amorphous CoFeZr alloy, and the second one (x ~ 40) nearer the percolation threshold - coincides with the phase transition of nanocrystals from hexagonal to cubic structure.