Rev.Adv.Mater.Sci. (RAMS)
No 3, Vol. 15, 2007, pages 208-214


A.M. Saad, V.A. Kalaev, J.A. Fedotova, K.A. Sitnikov, A.V. Sitnikov, Yu.E. Kalinin, A.K. Fedotov and V.A. Svito


The 5 to 15 μ thick nanocomposite films (Co0.45Fe0.45Zr0.10)x(Al2O3)1-x with 30 < x < 65 at.% sputtered in a chamber evacuated with pure Ar gas were studied using Mossbauer spectroscopy, magnetization, complex magnetic permeability, and magneto-force microscopy (MFM) measurements. In particular, the films with x < 40 at.% displayed superparamagnetic state at room temperature (the lack of sextets in Mossbauer specta, non-hysteresis character of the magnetization curves, invariability of real μ' and imaginary μ'' parts of magnetic permeabilities with x and high resistivity. Near the percolation threshold ( x ~ 40 - 45 at.%) Mossbauer specta displayed features of the ferromagnetic sextet and the values of μ' and μ'' increased, approaching the maximum, as x increasing due to the decrease of inter-particle distances. Moreover, effects of dipole-dipole and exchange interactions of the nanoparticles resulted in the nucleation of the magneto-ordered granules (magnetoclusters) including a few metallic nanoparticles. The MFM allowed to visualizing the presence of magnetic labyrinth-like magnetic contrast that was formed by the metallic nanoparticles near the percolation threshold. At x > 45 at.% the films behave like the "bulk" ferromagnetic sample with occasional inclusions of dielectric phase.

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